He seems to have a lot of acquaintances in the arcade and gaming centers, where he spends much of his time.This is clearly mentioned in the light novels.
Soubu High School Edit
They made their acquintance or acknowledgement of each other at the service club, intimes of Hayato's request to solve the chain message.Hayato appologised to Yoshiteru for interupting him by mentioning his name correctly, This made Yoshiteru happy for being recoganized by the popular student of the school who purposely/unknowingly mispelt Hachiman's name.
Intimes of Tashi's request, Yoshiteru along with Hachiman were jealouse and angered by Yui's plan to use Hayato to induce love in Saki's heart. Yoshiteru made fun of Hayato after he was indirectly rejected by Saki. Hayato acknowledged yoshiteru for he partially saw through Hachiman's plan of using Yoshiteru during Botaish event. He also requested Yoshiteru help through Hachiman for events like Judo.
Hachiman was able to see the hidden talent in Zaimokuza, as he recommended him along with Ebina to the Athletic Festival committee to make all the events interesting. Zaimokuza also gives Hachiman a list of places to search Sagami during the closing ceremony of the Cultural Festival (Mainly the places where he hangs out at.) They are able to have comfortable conversations and are in good terms with each other.
In the light novel, Hachiman noticed that Zaimokuza was left out in the mentioned list of people by Yui to celebrate Hachiman's birthday. Hachiman also noticed him missing in the Chiba Village summer camp. Zaimokuza also cares for Hachiman; this can be seen when he was willing to hear his problems when Yukino and Yui decides to run candidacy. Along with that, he also offered his contribution in fishing out votes for Isshiki and shows concern for Hachiman In his method to help Issihiki.
He also indirectly blocked the way for others in the marathon so that Hachiman can have a private conversation with Hayama. He is also shown to follow Hachiman's plan without any hardships. In the drama C.D. Zaimokuza hugged Hachiman in an attempt to stop and console him from explaining his traumatic experience of giving a gift to a girl he liked.
Hayama and Shizuka) to refer Zaimokuza as the friend of Hachiman, much to the latter's annoyance.
Despite all that, she does offer her assistance for Zaimokuza's request like reading his script throughout the night without sleeping, playing strip Daifugo against Yuugi Club, etc.
Zaimokuza on the other hand is completely bad with the interaction of girls which is clearly visible at the time of his first visit to the club, avoiding any conversation with Yukino. but that is later seems to disappear at the very least with the service club members