Almost all characters who interact with him personally show their true natures to him. At the very least when they are privately taking to him.
Both of Hachiman's parents are unnamed (not introduced to audience/readers) and are working in a corporate company, so they are always either late or outside, thus never shown in the series, to which Hachiman refers to as corporate slaves. It was mentioned that they never celebrated Hachiman's birthday, but they went out shopping during Komachi's birthday. Most of the time it was mentioned that they were scolding Hachiman for his laggness. They are mentioned to sleep till afternoon during their weekends.
In the light novel, it was mentioned that their father is very protective of Komachi to the point that he claimed that he will kill any boy who attempts to be close to her, even her older brother. Furthermore, his father didn't seem too fond of him as he is to Komachi. However, they did become involved in father-son recreational activities such as playing table tennis when Hachiman was younger.
His mother is more lenient and kind to him than his father. His mother was introduced in the light novel Volume 3 Chapter 3 and was also mentioned in Season 2 Episode 7. His mother is mentioned to wear glasses. Her kindness for him is shown in the series from time to time like cleaning his room without him even asking, putting a blanket while he's sleeping, warning him not to involve in any other accident etc. She is also mentioned to be broad-minded, as she arrange the stack of Hachiman's porn magazine which she found in his room while cleaning without saying anything. However, during dinner she gave him a death glare for him to be silent.
The power/privileged/social ladder in Hikigaya household is as follows:
Cat → Komachi → Mother → Father → Hachiman
In the OVA, Komachi mention about their grandparents, she says they are sweet, but Hachiman explains that they tend to be sweeter with the younger one.
Hachiman has shown to care for his sister to a great degree and some people, even Komachi herself, view him as a siscon because of it. He is also very protective of her as shown on how her friendship with Taishi Kawasaki makes him jealous to the point of adding Taishi to his "Unforgivable People List".When Komachi was in elementary school, Hachiman did all the house chores which are now done by Komachi. Hachiman also expresses how his relationship with Komachi when they were younger was completely non-existent.
Komachi is the only person Hachiman is willing to openly talk to about his personal problems. Though his rotten personality is something Komachi learned to deal with, she also has her limits and can be truly bothered when Hachiman acts slightly more indifferent to her than usual. Though she can hold a grudge about it for days, she also forgives him easily with just an apology from his part.
Komachi usually pairs Hachiman with Yukino and Yui at every chance she gets in order to cure his rotten personality. The two of them also have a running gag where they express their love for each other and call it a "point system" where the more lovable the phrase, the more points they get.
Soubu High School
In Season 2 Episode 8, Hachiman feels that if he was born 10 years earlier and met Shizuka 10 years later, he probably would have fallen madly in love with her.
Once during the cultural festival, Yukino asked Hachiman to signal Sagami to wrap up through the PA system of intercom which later became their usual banter until P.A person informs Yukino that their conversation can be heard by all in the intercom.Hachiman asks her to become his friend twice but was rejected. For the second time, Yukino immediately rejects him saying it is impossible for them to become friends, this time with a warm smile and in a friendly manner. Despite rejecting him as a friend, however, she still trusts him to a high degree (e.g. the Sagami case) and finds his social suicide plans 'irritating'.
After they have spent more time with each other, she tends to shows her feminine side to Hachiman whenever they are alone. She admires Hachiman because he can be himself, and she expresses a desire to obtain something that Hachiman does not have. During Tobe's request,she showed her cold side to Tobe for bad-mouthing Hachiman, almost rejecting to take up his request.After the completion of Tobe's request, Yukino expressed her hatred for Hachiman's method, which she describes as an unexplainable feeling by bringing her hand to her heart with cold eyes. She was flustered by Hachiman's plan for Iroha's request, rejecting it with a much more hostile emotion by giving every possible reason she could think of to oppose it at that moment. After Hachiman's emotional and tearful request to the club was completed, Hachiman thanked his club members to which Yukino states that the request is not over and that she will fulfill his request, a statement that somewhat shocks Yui and puzzles Hachiman. She tells Hachiman that she is beginning her search for it and will not follow her sister's shadow, and admits that she requires his help to achieve it. She then declares that she will stop hiding behind her sister's shadow. It is clear that Yukino views Hachiman in a greater light of high capability in the same standard as her sister, Haruno, whom she is envious of and looks up to most and vows to gain something that both Haruno and Hachiman doesn't have, so that she can save something. When Hachiman questions about its meaning, she simply stays silent and expresses a warm smile.Their relationship and jabbing were restored back afterwards. Hachiman also buys Yukino a pair of PC glasses as a birthday present.
In episode 11 of the second season of the anime (adapted version of Volume 10 ), when the rumor of Hayama and Yukino being a couple spreads throughout the school, Hachiman clearly feels disturbed over the rumor itself despite knowing it to be false. He tells Yui that he cannot imagine Yukino dating anybody, stating it was because of her social awkwardness, but Yui had suspicions that it was for another reason and was disturbed by it. It is also hinted that Yukino has developed a crush towards Hachiman over the series, even though she has not stated to Hachiman himself as her friend yet.
In the light novel version, during the marathon, after a conversation with Hachiman, Hayama questions Hachiman after some thoughts and suspicions of whether Hachiman is disturbed by the rumor. But, Hachiman got flustered in response and was unable to answer, to which Hayama laughs amusingly.In episode 12 of the second season of the anime ( adapted version of Volume 11), when Kaori wonders whether she once gave Hachiman any Valentine chocolates, she, Yui, Saki and surprisingly Tamanawa looked up curiously. When Kaori offers to give Hachiman some afterwards, she and Yui glare in jealousy. In the same time, Haruno recollects the time when Yukino gave Valentine chocolate to Hayato in their younger days, attracting equal attention where Hachiman visibly tries to act natural while Yukino worriedly glances at Hachiman along the sides and Yui notices both Hachiman and Yukino's behaviour.
In episode 12 season 2, when Kaori wonders whether she once gives Hachiman any Valentine chocolates, she, Yukino and Saki seem curious. When Kaori offers to give Hachiman some afterwards, she and Yukino look jealous.Due to Hachiman's (largely mistaken) belief that Yui's feelings for him are due to guilt, he indirectly rejects her; believing that he she was better off not knowing him at all for her own good. and thus indirectly rejected Yui, thinking that he would cause trouble for her. Yui tries to convince him otherwise, but Hachiman remains steadfast in his belief that her interest in him wasn't real; the indirect rejection reducing her to tears.
The strain in the relationship is repaired after the misunderstandings are cleared up with Yukino's aid during Yui's impromptu birthday party. It is relevant to note that Hachiman's actions during this arc were based upon his experiance with Orimoto, a girl he confessed to in middle school due to his mistaken impression that her kindness towards him was out of romantic interest. Because of his trauma that was created from the bullying following his rejection, he viewed Yui's kindness towards him in the same light. This attitude is, for the most part, gone once he reunites with Orimoto and they make amends for the past.
Hachiman didn't know what to give for her birthday hence presented her a dog collar for her pet Sable, Which Yui mistakes it for necklace at first. Yui is one of the few to have Hachiman's personal number and Mail ID (while the rest are Shizuka, Zaimokuza, Saika and Hayato). And it is interesting to note that Hachiman called Yui by her first name during her birthday party; albeit by accident while he was making fun of her poor naming sense.
Via Komachi's sly plan, both Hachiman and Yui went to the firework festival After the firework display, Hachiman walks Yui home where Yui cleared up the misunderstanding claiming that the accident wasn't the root cause for her behavior towards him.At the end, Yui seemed like she was going to confess to Hachiman, but an incoming call form her mother interrupts her. Although she seems determined to ignore the call and continue, Hachiman urged Yui to take the call, probably because he realized that Yui was going to confess and decided to prevent it. After ending the call, Yui realizes Hachiman's feelings and just says goodbye to him.
In the cultural festival, Yui offered Honey toast to Hachiman which she herself shared with him in the reception table of her class. When Hachiman questions about the conversation of Yukino and Yui, Yui states that she wishes to wait for Yukino since she is trying her best to open up to them. But she won't wait for someone who won't even try.When Hachiman wanted to pay for the honey toast, She asked him to take her out to pasela. But Hachiman requested time to think to which Yui nods happily.
Yui paired up with Hachiman during her field trip where she mostly hangs around with him when the group was lead to be paired.After Hachiman stunt at the confession, Yui tried to maintain her smile and later burst to tears asking why he can't understand others feelings.and asked him that he should stop doing it. Later both of them developed the habit of going to club together from class.
In the later series after Hachiman's desire for genuine things, Yui asked Hachiman's desire for Christmas present using a hand Pan-san puppet imitation but blushes away later remembering Hachiman's request to the club.Yui again expresses her wish of visiting an amusement park, to which Hachiman recollected His's promise of taking Yui out during the cultural festival for the honey toast. And promises to go to the nearby amusement park with her someday.
Yui later was shown to observe the romantic tension between Yukino and Hachiman which she suspects and became visually sadenned. In episode 13 season 2, Yui finally planned to go on the promise date but invited Yukino along where she wished for their status quo, which was rejected by Hachiman. Yui planned to take all by winning the battle royale challenge which was unopposed.
Hachiman once pairs up with Saika for tennis. Saika also asked Hachiman personally to join the Tennis Club to help raise their strength. Hachiman has kind of a crush for Saika, he has to stop himself from falling for him. He was in the same class as Hachiman for two years.
Saika often shows interest in teaming up with Hachiman in many occasions like field trip, summer camp etc. Saika was able to tell when Hachiman was depressed or feeling down and attempt to cheer him by taking him to the arcade. Saika was the first person to officially hang out with him, In the Light novel, they went to movies in summer vacations and later joined with Zaimokuza. Saika and Yoshiteru often invited to all partys by the service club
They seems to have comfortable conversation and are in good terms with each other. Furthermore, after the rooftop incident, Zaimokuza are among those who know the real truth behind Hachiman's provocation on Sagami, and admires his courage as he gives a nod of approval and a smile. He seems to have better understanding of each other. Zaimokuza also shows his part of concern which can be seen in their conversation in phone during Isshiki's request where he ask if Hachiman is okay with what he is doing.
Hina Ebina's yaoi play during the cultural festival, much to their dismay.
Hayato once revealed that he was unable to solve Yukino's bullying problem by her jealous classmates at their previous schools and believed that if Hachiman attended the same former schools as them, things would turned out differently. Hayama seems to know something that Hachiman didn't, as he says that "Now I know why she looks out for You" which puzzled Hachiman but he lost the chance to clearly ask Hayato.
At first, Hayato acknowledged and credited Hachiman for the brilliant solution for the false chain message incident, and even thanked him for it, which short lived due to the Chiba Village summer camp and Sagami incidents. Even though he can understand the reasons behind Hachiman's methods, he refuses to acknowledge him.
At the end of cultural festival committee members meeting for the slogan selection, he simply left Hachiman without even sparing him a glance out of distaste for the former's sarcastic remark on the slacking off committee members. During the infamous rooftop incident, he violently grabbed the front of Hachiman's shirt and told him to cease talking, not only it sounded extremely unpleasant, but because he aware of his true intention, and didn't find it appreciable at all. When everyone on the rooftop left, Hayato asked Hachiman whether it was the only way for him to do things in a tone of deep disgust..
Hachiman feels that Hayato's method are not practical or preferable. On the other hand, Hayato despises Hachiman's way of solving problems, e.g; breaking the relationships between Rumi's peers by exposing their true selfish nature, the cultural festival slogan containing thinly-veiled criticisms on slacking off committee members, provoking Sagami harshly, etc.
Later, he defended Hachiman by saying, "Well, he’s just got a bad mouth. If you actually talk to him, he isn’t really like that”. However, most felt that Hayato is a very kind person for standing up for Hachiman. Furthermore, he was willing, albeit with a heavy heart, to invite Hachiman through Yui to the party he hosted for celebrating the success of the cultural festival. But it was turned down by Hachiman.
Hayato also find Tobe's Somethingtani-kun joke on Hachiman's surname were not very amusing, causing Tobe to cease joking about it. He defended Hachiman again when they were together during the double date with Kaori Orimoto and her friend, when she and her friend belittled Hachiman by recalling the embarrassing past of him during the middle school by stating coldly that Hachiman has befriend girls who are far more better than both of them (Yukino and Yui) in the presence of the two, causing Kaori and her friend to be embarrassed of their behavior and cancelled the date.
The main clash between them is their approach and view of life, even-though their goal is the same. Hayato believes in an idealistic world, where nobody gets hurt and everyone get along well, but Hachiman sees the world for its reality. Most of Hayato's method didn't yield the desired result while Hachiman's method does, but his methods were despised by Hayato..
Hachiman, however, refuses to do anything with Hayama, as he sees that Hayama's action shows only pity towards him, The thought of being pitied by someone always irritates Hachiman and thus he always rejects it and the people who show it towards him.
In Episode 10 of seson 2 ,Hayama also mentions that he might not helped Iroha in the student council works. Hayama privately talked to Hachiman of his reasons for rejecting Iroha in the destiney land.and praised the later for his ability to change people. He also adds on that his reason for praising Hachiman is to satisfy himself.
Later in Episode 11 of season 2, For Yumiko's request Hachiman prescribe Science as path course for Hayama in the maraton by pointing out the benefits for Hayama. To which Hayama claimed that he hated Hachiman and was not possible for them to get along. Because he often feels like losing to the latter and surfaced his inferiority complex towards Hachiman, something that Hayama can't cope with. In order the deal with his feelings of losing to Hachiman, Hayama attempts to elevate Hachiman to his equal, so that he could accept his losses to the latter. But vows not to follow Hachiman's idea.
Hachiman replied that the feeling of hatred is mutual. As Hachiman feels that Hayama is not doing the necessary in times of need, but stays aloof. However, his supposed hatred towards Hachiman should be taken with a grain of salt, and it is remained unclear whether it was literal.
Hayato admires Hachiman's ability to change everyone around him. While Hachiman addresses Hayato as a nice and good guy so that Hachiman can be satisfied by his method of losing publicly to Hayama as stated by Hachiman in light novel. Perhaps sensing this, Hayama tells Hachiman that he is not as much of a good guy as the latter seems to think, to which Hachiman does not respond. Thus an unbalanced and half-hearted relationship exist between them.
In the haunted house during the field trip,she was seen clinging to Hachiman's blazer. Saki also contributed her help to save the service club. It is also seen that Saki knows Hachiman's leadership abilities when she said she wants Hachiman to Student Council President although she shrug it off as a joke because Hachiman says that not many will vote for him.
In episode 12 season 2, when Kaori wonders whether she has given Hachiman Valentine chocolates before, Saki seems curious. Saki also pointed out to Hachiman that, she packed some of her own hand made chocolate along with Keika's valentine chocolate for Hachiman.
episode 10 she writes Hikigaya's last name correctly on the board for her yaoi play.She also wrote Hachiman's first name correctly in the survey by service club for Love and Marriage column of a magazine.She seems to like the idea of Hayama and Hachiman being a couple due to her love for BL and she always make strange giggle whenever they are seen together.This intention about them started only after the cultural festival and not before that.
When she learns that Tobe is about to confess to her, she indirectly requested Hachiman to stop Tobe from confessing to her in-order to maintain her status quo.She thanked Hachiman personally when it is done. It must be noted that she is the second person to thank Hachiman aside from Hayama (chain message incident).Ebina eventually told him that she hates herself for always being selfish with her desires and that she is rotten.
In light novel, after the field trip incident she freely speaks her mind to Hachiman only when they are alone.She even gives him hint to meet her alone to discuss about the issues of service club's requests regarding her clique.
Tobe is the first person to mistakenly address him as Hikitani, which becomes an informal nickname, which results in his clique members to call Hachiman the same. After the Chiba Village summer camp incident, he started to have a very negative opinion on Hachiman, and felt that he is seriously terrible person.
At the end of the cultural festival, he shared his opinion to everyone within earshot. He even made fun of Hachiman by referring him as Somethingtani-kun . In the Service Club, he refused to state his request in the presence of Hachiman as he felt the latter had "zero reliability". As the series progresses, Tobe started to understand Hachiman's better, which can be seen during the school field trip. He believes Hachiman's indifference and frank comments is due to him looking out for him, a fact that he appreciates since Ooka and Yamato's encouragement for his confession is because they think it's fun.Tobe alos invited Hachiman to play with him in the lodge of the field trip but Hachiman declined.
After the field trip Tobe casually talks to Hachiman in a friendlier manner than before, hinting that all his negative opinions on the latter has vanished. But he still believes Hachiman's name is Hikitani and even continues to address him as such, much to the former's irritaiton. Hachiman also begin to see good points in Tobe and describe him as a nice person in his private conversation to Hina but still felt him to be annoying .
Iroha's personality reminds Hachiman a lot of himself, and he makes frequent comments about their affinity with one another; at one point commenting on how he found her natural malicious smile much cuter than her usual appeal. However as they get to know each other more, Hachiman's initial negative impression gradually changes. Iroha seems to be more free and at ease with Hachiman than any other character, even being her true self with him which suprises Hayama but annoys Hachiman to some degree.
After Iroha became the president, Hachiman begins to feel guilty for pushing the role onto her and volunteers to help her out. It has come to a point where Hachiman naturally treats Iroha much in the same way as he treats Komachi, always giving into her unreasonable requests because he feels like he has a responsibility to look after her. Iroha begins to rely on Hachiman too much. When Hachiman refused to help her anymore, she goes to the extent of asking Shizuka for Hachiman's help.
A turning point in their relationship is after she was rejected by Hayama. While being comforted by Hachiman, Iroha shifts the conversation to be about him, and reveals that she overheard Hachiman's desire for something "genuine" during his request towards the Service Club. Hachiman embarrassed by the fact that she listened to his moment of vulnerability, asks her to forget about, and she replies that she won't forget about it, and she is unable to. She declares that she also wants something genuine, and after Hachiman states that she is a pretty amazing person, she claims that it is his fault that she became this way; and tells him that he needs to take responsibility.
A running gag of the series is her misunderstanding of Hachiman's words as a confession towards her and a quick rejection, to which Hachiman eventually gets used to. In episode 12 of season 2, (an adaptaion of Volume 11) Iroha feeds Hachiman a spoon of chocolate syrup. When Kaori asked Hachiman wether she ever gave him any Valentine chocolates before, Iroha look surprised and looked up curiously. Iroha also gave a bag of Valentine's Chocolate to Hachiman and asked him to keep it a secret from everyone else, before departing to compete with her love rival Yumiko.
In light novel Volume 10.5, the two even go on a date, where Hachiman admits (albeit internally) that he finds Iroha to be cute even with her sly personality. During the date Iroha showcases her understanding of Hachiman's mentality when he suggests going to two separate movies and meeting up later; her comment in response showing that she is very much on the same wavelength as him. After a match of table tennis Hachiman complains to Iroha about her being "unfair", and she replies that being unfair makes her more of a woman; afterwards she whispers into his ear and states that he is the only one she will act this way towards.
Haruno also knows about the car accident incident that involves Yukino, Yui and Hachiman, which she states it as a joke at firework festival without realizing that Yukino didn't informed them.She quickly stands for Yukino saying she was not driving the car and was at the back seat
Haruno sees Hachiman as an intriguing person, most notably due to his incapability of understanding the emotions of other people; a trait that made her declare him a "monster of logic". While Haruno usually takes a very provocative and aggressive demeanor in the presence of Yukino, she is notably more casual when alone with Hachiman.
Haruno also sets-up Hachiman and Hayato on a double date with Kaori Orimoto and her friend and even followed them without their knowledge.
Hachiman despises her and is frightened by Haruno's sly and fake personality, stating that after he was able to see through her facade, she hadn't bothered trying to hide her inner face ever since.
Volume 9). She seems more open to Hachiman during their conversations, since both of them are fellow loners and ostracized by their peers. However, after the test of courage incident, she didn't speak to him and just walked past him; it is likely she realized that Hachiman planned that all.
During the Christmas collaboration event between Sobu High and Kaihin Sogu High. Hachiman and herself were making Christmas tree decorations together. Hachiman sees that his method did save her from bullying, but he feels that it was not been enough as her solitary aura still remains. Her status is what gave Hachiman the final push to realize his methods were not effective, solving the short term issue but not truly doing anything to fix it.
Hachiman made an acquintance with Taishi through Komachi with the request to find her sister's night activity who happen to be Hachiman's classmate. Though Hachiman is cold towards to him due to his closeness to Komachi, Hachiman took most steps to resolve his issue and succed in finding a suitable solution. Hachiman was able to understand Taishi better than Saki. Hachiman also offered advice about High school choice
Taishi is respectful towards Hachiman, as he frequently calls him big brother and held him in high regard.
Keika is fond of Hachiman and calls him Haa-chan. Mostly they play when ever they meet. In light novel Keika offered Hachiman a bag of Valentine chocolates and kept on clinging to him.
She is interested in getting to know Hayato through Hachiman and Haruno. A glimpse of Hachiman's past by Kaori treatment of Hachiman is shown throughout the date. And it is made obvious that Hachiman no longer holds any romantic feelings for Orimoto anymore.Due to the events of the double date and the Christmas collaboration event of their school, Kaori's attitude towards Hachiman seems to have changed and is more considerate about what she says about him because of Hayama's criticism, though she still maintains her casual nature around him. She states that she might have been good friends with him and thus want to patch up the relationship with him. She even offered him valentine chocolate in the per-valentine collaboration event, But states that she cannot view Hachiman in the boyfriend's light since she feels that he lacks the boyfriend material.