Family
Yukino's father is a member of Chiba prefectural diet. Yukino's father is also the CEO of a construction company. Her father seems to be more lenient than her mother as he lets Yukino live alone in an apartment. It was mentioned by Haruno in Episode 3 of season 2 (adapted from Volume 8 Chapter 3 ) that Yukino sent a souvenir by courier to their house which Haruno explains that Yukino hates them but doesn't want to be hated.
Mother
Voiced : Kikuko Inoue
Yukino's Mother
Her mother was introduced in Episode 10 of season 2 (adaptation of Light novel of Volume 10 Chapter 2), where she came to take her daughter and Hayato to their traditional new year feast. Haruno first mentions her mother in Episode 9 of Season 1 ( adaptaton of Volume 5 Chapter 6) as scarier than herself and takes all decision of the family, enforces the others to follow while the rest have no choice but to compromise with her decision and follow.
Yukino is mentioned to not be in good terms with her mother by Haruno or compromising with her mother's wishes. It was also mentioned by Haruno that her mother was against Yukino's idea of living on her own. The strain in the relationship is clearly shown in the anime.
Later, In Episode 11 of Season 2 (adaptation of Volume 11), she came to visit Yukino to her apartment but had to wait in the limo since Yukino was taking her time to get there from the community center where she expressed her concern for Yukino being late and also expressed her grief of Yukino's career choice which she heared from Haruno, She later blames herself for letting things get this far. Yukino promises to explain herself and asked her mother to leave.
Haruno Yukinoshita
Yukino orders Haruno as committee vice-president
She is the older sister of Yukino. Haruno is known to be more outstanding than her sister, and Yukino holds strong animosity towards her. Haruno seems to like pairing up Hachiman and Yukino together, even going to an extent of scaring Yui to stay away from Hachiman.
Haruno teasing hachiman and yukino as a couple
In Episode 9 of season 2, it is later revealed that most of Yukino's fearful and unsociable behavior are due to her sister's meddlesome behavior towards her. Whatever Haruno sees cute in Yukino is the same thing that she hates about her. When Yukino questions Haruno about Hayato's career path choice, Haruno answers coldly with a smile to find it herself.
In Episode 11 of season 2, Haruno came to stay with Yukino in her apartment by her mother's order.
Soubu High School
Hachiman Hikigaya
Yukino and Hachiman
Hachiman nicknames Yukino "Ice-cold Beauty" for her personality from the start. Yukino hates how Hachiman accepts and affirms weakness by loyalty to status quo. While Yukino does not recognize Hachiman as a friend, she acknowledges him as an acquaintance. Yukino recognizes Hachiman from the car accident, but hid the fact from him when Hachiman joined the service club, pretending to not know him. After realizing this, Hachiman slowly distances himself from Yukino
Hachiman and Yukino in cultural festival inspection
Over the course of the series, the relationship between the two seems to soften slowly. Yukino starts to warm up to Hachiman and even manages to eventually smile at him. She even shows her girly side to him. She is also fond of teasing Hachiman by "blaming" him to be the cause of some incident. For example, she claimed that her sleepiness vanished after seeing Hachiman's face, and Saki Kawasaki's change of behavior started after she became a classmate of Hachiman etc, much to his irritation.
Hachiman and Yukino
Although she still does not recognize him as a friend, she starts to see Hachiman for who he is and has somewhat started to develop a possible crush on him but this is somehow restrained as in the novel, it is strongly hinted that she realizes about Yui's feelings toward Hachiman.
Hachiman giving Yukino a Pan -san doll from a crane game
Hachiman and Yukino along with Komachi went out shopping for Yuighama's birthday in which Komachi slid away creating a date-like situation. Sensing the suspicion of the shop assistant and the surrounding customers, Yukino told Hachiman to pretend to be her boyfriend. In Chapter 4 of Volume 3, Hachiman won a Pan-san stuffed toy for Yukino from a crane game using his underhanded technique.
Episode 8 of season 2 (Adaptation from Chapter 6 of Volume 9 of the Light novel) shows how Yukino's icy behavior is melting. She was about to burst into tears when Hachiman came for a request in helping Isshiki and said that he wanted "something genuine" (implying relationships and feelings). For the first time in her life, Yukino feels very emotional. It is hinted that she has started to lose her "ice queen" personality especially to Hachiman but only when they are alone. She smiles and chuckles often in their conversation lately.
Yukino and Hachiman riding a ride in destiney land
In Episode 9 of season 2 (Adapted from Volume 9 of light novel), in Destiny Land, both Yukino and Hachiman got separated from the group due to the crowd and went on a ride together, where she asked Hachiman to save her someday without any other words in succession. There she opened up a little about her past to Hachiman and said she wants something that both her sister and Hachiman don't.
In Episode 10 of season 2 (adapted from Volume 10), Hachiman bought PC glasses for her birthday to which Yukino nervously waits for Hachiman to compliment hew on how the specs look on her. This is rather unusual, since she normally thanks any compliment in the past like her apron purchase in time of Yui's birthday shopping and also at the time of her maid outfit in Saki's case. This makes Yui worried swifting her glance between Yukino and Hachiman. When Hachiman volunteered to carry Iroha's belongings, both Yui and Yukino stayed silent. This vaguely hints that they were jealous.
In Episode 11 of season 2, Yukino is shown to treat the wounds of Hachiman in the infirmary which resulted during the marathon. During the treatment, they had a long time staring at each other flustered. This was abruptly stopped by Hachiman thanking her. This was also when Hachiman asked her about her career path to which she was surprised to hear. She says that she'll be taking liberal arts. During a meet-up between Haciman and Haruno, Haruno asks if Yukino told him of her career plan to which he said yes. Haruno indicates that Yukino trusts him but he denied it by saying it's not trust. Haruno implies that it is indeed not trust but something more cruel.
Kaori asking Hachiman whether she gave chocolates before
In Episode 12 of season 2, Service Club gets a request from Yumiko, Saki, Ebina and Iroha regarding having problems making or giving valentine chocolate, for which Hachiman suggests to make it like a event. They later held Pre-Valentine Cooking class where Haruno, Service Club members and others are invited. When Kaori asks Hachiman whether she gave chocolate to him before, everyone is surprised and he tells she did not.
She replies saying i'll give you this year, making Yukino and Yui jealous.
Yukino looking for Hachiman's facial reaction
Next, Haruno says directing towards Hayato that he received chocolates from Yukino long time back, much to Yumiko and others surprise. For a second Hachiman flinches and instantly restores his composure when Yukino searches for any reaction given by Hachiman on Haruno's statement. Hayato covers Haruno's statement by saying she gave it before starting of grade school to both Hayato and Haruno.
Haruno commenting on their relationship
When the event was near the end, Hachiman tastes the chocolate cupcakes made by Yukino and Yui. Haruno comes in and asks Hachiman that is this the real thing that he wanted and says that he has disappointed her as she thought of him as a bit more interesting person to do things like that. And says that the way they are now is lame, and that she prefered the old Yukino. Even though it's not completely elaborated of the meaning of her comment, Hachiman's soliloquies on Haruno's comment after she left implies that, Haruno meant that the Yukino before was not someone who would have a pretence relation and would come straight with whatever she had to say.
Even though Yui,Yukino and Hachiman knew each others feelings, they didn't want to destroy the friendly relationship which was built over their time being together in club and continued it as though they were pretending not to know it. This pretence relationship was what Haruno called lame. By saying that she preferred old Yukino more, she forced them to break out of this loop of pretence relation which left them pretty much depressed for the whole day.
In the Episode 13 of season 2, after the events of episode 12, they somehow continue their relation as it is, but after school Yukino stops Hachiman and holds her hand on her bag but is hesitant to move forward or say anything, but it is implied that Yukino wanted to give Hachiman the chocolate she made for Valentine's Day (probably home made chocolate) but she didn't because Yui saw her chocolate and then things got awkward. Yui then tries to leave them alone, but Yukino stares at Yui implying not to do so.
Then, Haruno comes by car to say that her mother is calling Yukino and starts a argument with her. After Haruno says to Yukino that she doesn't have a personality to define herself with, Hachiman snaps a bit and stops their argument. Haruno returns by herself, but since it had become pretty heated up between her and Yukino, Yui suggests Yukino no come to her house.
Yukino stays over for night at Yui's place and Yui tells Yukino that she has decided what she wants and tells her to come to a date with her and Hachiman. From the viewer's point of view, trying to find about Hachiman's feeling is pretty much tough. Even though events from the episode 11 and 12 implies that Hachiman might be shown to care for Yukino to great extents, but at the same time the random calls for dates which Hachiman throws towards Yui with some or other reasons is something that can't be ignored. On the date, Yui declares that if she wins in the contest that Hiratsuka had given at the starting of Hachiman's entry to the club, she will take everything because that is what she really is, a selfish and greedy girl. She doesn't say anything specific about what she meant by everything. Hachiman's soliloquies about the same, saying if she had mentioned what it is it would confirm everything. Yui adds that she wants the relation they are in to continue, and asks if Yukino would be fine with it. Yukino strains to answer hesitantly, teary eyed and forces herself to try to say that she would be fine with it,but just before she finishes Hachiman disagrees to Yui and says that the relation Yui mentions is nothing but a deception to himself and others and doesn't want that. He adds that we have to think more and find a satisfying answer.
In 2nd season OVA, there is a scene in which Yukino keeps walking and then stands beside Hachiman when they are in a shopping mall, and goes awkwardly silent.
Yui Yuigahama
Yui and Yukino playing in the river.
Even with Yukino's cold and brash personality, Yui still views her as a dependable friend - affectionately calling her "Yukinon" and sometimes hugging her when feeling thankful. Over time, Yukino starts to think of Yui as a friend. Yukino also celebrated Yui's birthday in sly manner of rejoining her in the club, as she didn't want to lose her friend Yui or replace her with anyone.
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Yui hugs Yukino in Destiny Land.
Yui is the first best friend of Yukino. She considers Yukino's straightforward personality and harsh honesty as 'cool'. They played together in Chiba Summer camp at the river bank and also with fire crackers at the end of the camp. Yukino brought Yui an apron as a birthday present.
Yui and Yukino having lunch in the club
They get along well, to the extent of eating lunch together in the club room, sleeping over at Yukino's house, exchanging clothes, and regular emailing each other. In Episode 13 of season 2, Yui invited Yukino to her house to stay over at her place for the first time which is further insisted by Yui's mother who address Yukino by the same nick name as Yui.
Yukino also threatened Yumiko in a double tennis match for causing an event that led to Yui get hurt, where Yukino almost addressed Yui as her friend
Yui seems to understand that, Yukino is trying her best to get- along with her and decides to wait for her.They seems to enjoy hanging out together. On the third day of the school field trip, they spent time shopping together. It is clearly hinted that both of them hold their feelings for Hachiman in concern for each-other.
Shizuka Hiratsuka
Shizuka is the adviser of the service club in which Yukino is the president. Shizuka seems to be genuinely care for Yukino's well-being. Shizuka describes Yukino as quiet talented, kind and correct. She also see the flaws of her way, just like she can see Hachiman's way. Shizuka worries and cares about Yukino to a great extent. Shizuka also understand Yukino as she was able to provoke Yukino to take the battle royale challenge.
In the Light Novel, it was mentioned that Shizuka made Yukino become the member of the service club using Yukino's twisted sense of "nobleness oblige". Shizuka also sometimes teases Yukino with Hachiman as a pair. Shizuka also knows Yukino's ambition and wishes Yukino not to be a second Haruno and wanted her to work on her strong points. In Episode 1 of season 2 (adaptation of Volume 7) She gave Yukino her coat and asked her to accompany her and Hachiman to the ramen shop for ramen as a form of bribe to prevent her from revealing that Shizuka had snuck out.
Meguri Shiromeguri
Meguri showing concern over Yukino
Meguri recognized Yukino as Haruno's sister and requested her to take the role of committee chairperson which she turned down. Meguri and Hayama Hayato have shown concern for Yukino's well-being when she attempts to take on the majority of the work for the cultural festival. She also has expectations for Yukino to succeed her as Student Council President, but it is in vain.
Hayato Hayama
Hayama is the son of the legal adviser of Yukino's father and a former grade school classmate as well. The both of them are childhood friends. It was hinted that, Hayato failed to protect Yukino when she was bullied/ostracized in the past. But all the attempts made by Hayama to mend the relation failed. It was mentioned in Light novel that Hayama used to call Yukino by her first name in the past just like he addresses all girls in school by their first name, but now he addresses her by her last name. Hayato also noticed Yukino's change of not following her sister's path but doesn't feels satisfied with the rate of her change.
In the past Yukino was mentioned to give Hayama some valentine chocolate as mentioned by Haruno but Hayama explains that Yukino gave it to both himself and Haruno in times of their elementary school which Haruno didn't deny it.
Others
Yukino, despite being a loner has a good reputation among her classmate. In light novel it was mentioned that in case of grouping for any events, Usually girls from the group ask her to join them and she used to choose which group she goes along with.Yui points out the reason for this as Yukino tends to give cool vibe and her class contains 90% girls.
Komachi Hikigaya
Yukino checking komachi's cat outfit
Yukino once mentioned that she was jealous of their good sibling relationship. They seems to be on a good terms, and Komachi has high respect for her. They freely talk about various topic. Yukino genuinely care for Komachi and also her academics like a mother. Yukino also freely ask help from Komachi for which she is reluctant to ask Haruno, such as shopping for Yui's present, in preparing a magazine as part of a campaign by the Chiba region to promote "Love and Marriage" to teenager, etc.
Komachi slyly set up a date-like situation between her and Hachiman. Yukino along with Yui and Hachiman selected Christmas present for Komachi. There are a lot of outing to which Yukino personally invites Komachi.
Yumiko Miura
Yumiko vs Yukino in Athletic festival
Yumiko feels to be rivaled by Yukino's popularity. From their first encounter, their ideals and point view clashes because Yumiko doesn't like to be criticized while Yukino is blunt and straightforward. Thus a great enmity developed between them, which grew in each encounter for various reasons. In Chiba summer camp, Yumiko while standing in defense for Hayama pointed out that she didn't like Yukino's character while Yukino retaliated by saying that she hates Yumiko. In the heated argument Yumiko cried after thirty minutes of word fight.
In Light novel, during tennis match Yumiko threatened to hurt Yukino but it backfired. After the rumor of Yukino and Hayama dating spread throughout the school, whom Yumiko has a crush on and friends with, enraged Yumiko grabbed Yukino's shirts collar which was blocked by Yukino herself. After all misunderstandings were cleared, Yumiko bowed her head and apologized to Yukino for all her past actions. To the surprise of all service club members, Yumiko also personally invited Yukino to the celebration of Hayama's victory in marathon, thus ending their enmity and are finally on good terms. Yumiko later requested the service club to help her make Valentine chocolate which Yukino personally helped her with, where they talk more casually than before. However Yumiko presented a shocked reaction, after learning that Yukino presented valentine chocolate in their younger days and releaved after the misunderstanding were cleared.
Iroha Isshiki
She had hints of jealousy towards Iroha's closeness with Hachiman. When Hachiman volunteered himself to carry Iroha's belongings, she and Yui went speechless.However Yukino begins to show her soft side for Iroha and views her as relying underclassmen and help her in many ways and most situation.