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 resents them but doesn't want to be hated.
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 on 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 on, 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 heard from Haruno, She later blames herself for letting things get this far. When Yui tried to defend Yukino, Mrs. Yukinoshita indirectly asked them not to interfere and leave to their home. Her eyes met Hachiman who immediately excused himself. Yukino later promises to explain herself and asked her mother to leave.
When her car passed by Hachiman and Yui while they are going home, Hachiman felt that Mrs. Yukinoshita was observing him through the one way vision window of the rear seat of the car, which sent a chill through his spine.
Haruno is the older sister of Yukino. Haruno is known to be more outstanding than her sister, and Yukino holds strong resentment and animosity towards her.
Similar to Hachiman's sister Komachi, Haruno seems to like pairing up Hachiman and Yukino together, but her efforts are more persistent as she even going to an extent of scaring Yui to stay away from Hachiman or get him to call her big sister both of which fail and annoy Hachiman and Yukino to no end.
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. It was revealed that Yukino stopped giving valentine chocolates to Haruno after not receiving any from Haruno.
In Episode 11 of season 2, Haruno came to stay with Yukino in her apartment by her mother's order.
Soubu High School
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 appear to recognize Hachiman as a friend, she acknowledges him as an acquaintance.
It is revealed that Yukino was in the car that struck Hachiman, which left him hospitalized for two weeks and set him on the path of being a loner. When they formally met, Yukino immediately recognized Hachiman from the car accident but hid this fact from him after Hachiman was forced to join the service club. She pretended not to know him, possibly out of fear of further isolation from someone, while he was aware of who she was because of her reputation but not her knowledge of the accident.
While Yukino was put off by Hachiman's attitude and he was hostile towards her condescending attitude, she was quite surprised by his intellect as he was familiar with certain books and quotes that she knew. As they were both loners who were ostracized by their peers and distant because of it, the two somewhat got along, due to their similar backgrounds. Hachiman tried to use this as a way to befriend her but he was immediately turned down by her as a result, much to his annoyance.
She also couldn't find a way to identify herself and her association as they were neither friends nor true acquaintances after she met his younger sister Komachi Hikigaya, while he was annoyed at her cold and condescending ways.
After Yui and Hachiman had a falling out, she asks him what occurred but isn't given an answer, so she has him help her in bringing her back. She nervously and blushingly asks him to go out with her on a "date", to his shock.
When Hachiman and Yukino along with Komachi went out shopping for Yui's birthday, in which Komachi slid away creating a date-like situation, much to Hachiman's annoyance. Sensing the suspicion of the shop assistant and the surrounding customers, Yukino asked Hachiman to pretend to be her boyfriend, to his confusion. However, she was surprised that he actually agreed since she had expected him to refuse. She was also flattered that Hachiman called her cute in an apron that she had picked out. Yukino had shown she had knowledge of Hachiman's accident after asking if he was a cat or dog person. Also, Yukino's sister had commented on their relationship while Yukino was rather shy to hear this. She was even amazed by Hachiman's ability to see through her sister's façade even giving him a compliment for looking through others.
She clung to him for aid when she was scared of a dog (later revealed to be Yui's dog which both of them recognized), these events showed she trusted him to an extent. Hachiman was very amused by her behavior as fear was something he didn't think she had.
At Yui's party, when Yui voiced her mistaken belief they were now dating, both mutually agreed that such a thing would never occur. She soon remarked on the wedge that drove Yui and Hachiman apart by stating that neither one of them was really at fault for the incident that injured Hachiman as he saved Yui's dog. Hachiman had noticed a remark with Yukino's statement, this was because she was aware of the accident.
Afterwards at camp, Hachiman noticed the black car that Yukino left in was the same one that struck him and realized Yukino was there. This was confirmed by her older sister Haruno Yukinoshita that she was in the car that struck him on the same day of his accident, Hachiman was deeply hurt that like Yui, she also withheld this knowledge from him. Having learned this news, he saw that his previous views of an honest and straightforward Yukino were wrong. As a result of this knowledge, he slowly distanced himself from Yukino, even though she had tried to explain herself for this after realizing that he had became aware of the truth.
Following this, he barely spoke to her at the club while she is shown to be somewhat sad about it, possibly meaning she was getting use to their interactions.
Over the course of the series, the two seem to rebuild their relationship and the standing between the two seems to soften slowly. After the festival, the two finally talk about the accident once Yukino states she wasn't lying about not knowing him in their meeting but says she knows him now. He offers to be her friend a second time but was rejected immediately, only in this instance Yukino states it is impossible for them to become friends, this time with a warm smile and in a friendly manner. It is then that Yukino tells him that she really didn't know anything about him, but she knows him now, since they have spent a lot time together in the Service Club. Thus, she indirectly tells him that they could theoretically be friends.
It later appears that he came to forgive Yukino for withholding the incident while she starts to warm up to Hachiman a little more even managing to smile at him, showing 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.
Although she still does not recognize him as a friend, she starts to see Hachiman for who he is and has even developed a crush on him because she knew that Hachiman has something similar to her and she barely can rely or believe him to help her someday. But this is somehow restrained as in the novel, it is strongly hinted that she realizes Yui's feelings towards Hachiman as well and she doesn't want to hurt her as they were one of the first to accept her.
In return, Hachiman is hinted to be aware of Yukino's feelings, due to studying the atmosphere around others and taking note of her sudden changes in her behavior. While Hachiman sometimes blushes around Yukino when they have a moment, he tries his best to restrain himself as he might not acknowledge her feelings as real because of his past failures with girls.
In Chapter 4 of Volume 3, Hachiman won a Pan-san stuffed toy for Yukino from a crane game using his underhanded technique.
It appears Episode 8 of season 2 (Adaptation from Chapter 6 of Volume 9 of the Light novel) how much of 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 conversations lately.
In Episode 9 of season 2 (Adapted from Volume 9), 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. Once there, she opened up a little about her past to Hachiman and said she wants something that both her sister and Hachiman don't. She also noticed that Hachiman and her have many common between each other. It is also noted that Yukino bought the photo of the two looking at each other that was taken, from when they were going down the water ride.
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 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 sifting her glance between Yukino and Hachiman. When Hachiman volunteered to carry Iroha's belongings, both Yui and Yukino stayed silent. This greatly 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 blushing full red. 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 Hachiman 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.
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 an 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, Yukino is seen surprised and he tells her she did not. When she replies saying "I'll give you some this year", this comment clearly makes Yukino and Yui jealous as seen with her staring at Hachiman.
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 Yukino gave it before starting of grade school to both Hayato and Haruno which Haruno did not refuse.
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. Haruno says that the way they are now is lame, as she preferred 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 pretense relation and would come straight with whatever she had to say.
Even though Yui, Yukino and Hachiman knew each other's 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 pretense relationship was what Haruno called lame. By saying that she preferred old Yukino more, she forced them to break out of this loop of pretense 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. After school Yukino stops Hachiman and holds her hand on her bag, but is hesitant to move forward or say anything. 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, urging her wordlessly not to do so.
In the 2nd season OVA, when they are in a shopping mall, there is a scene in which Yukino keeps walking near and standing beside Hachiman. The pair goes awkwardly silent.
At the end of Volume 14, Chapter 7, Hachiman confesses that he wants to get involved in Yukino's life—not as an obligation, but because he wants to. He knows that once he lets go of her, he will never be able to get her back. After a bit of an awkward yet heartfelt conversation, Yukino asks Hachiman to give her his life, and the two become a defacto couple.
In their first meeting, Yukino did not hesitate to criticize Yui but she was surprised that Yui called her amazing. Yui mentioned that Yukino was hurtful in statement but she was jealous that her casual display of speaking her mind. 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. At Yui's birthday party, Yukino brought Yui an apron as a birthday present. This touching sentiment earned her a hug from Yui who thanked her for her gift.
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.
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 nickname 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 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 ssee 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 "noblesse oblige". Once, Shizuka teases Yukino with Hachiman as a pair which Yukino didn't get the true meaning or deliberately acted so. 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.
In times of Christmas event, Shizuka told Hachiman about the possibility of some one inthe future may break Yukino's shell and understand her better but wants and wishes Hachiman to be that person. To help Hachiman in mending the service club relationship, Shizuka pointed out the reason which Hachiman overlook in taking up the Iroha's request, if he did it for Iroha or Yukin . Shizuka's words shocked Hachiman in realization of his possible miscalculation.
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 had expectations for Yukino to succeed her as Student Council President, but it is in vain.
Hayato is the son of the legal adviser of Yukino's father and a former grade school classmate of Yukino's 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 has failed. It was mentioned in Light novel, that Hayato 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 feel satisfied with the rate of her change.
In the past, Yukino was mentioned to give Hayato some valentine chocolate as mentioned by Haruno but Hayato explains that Yukino gave it to both himself and Haruno in times of their elementary school which Haruno didn't deny it.
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.
Yukino once mentioned that she was jealous of Hachiman and Komachi's good sibling relationship. They seems to be on a good terms, and Komachi has high respect for her as she has elegance and carries on an intelligent attitude. They freely talk about various topics, Yukino shows she genuinely care for Komachi and also helps with her academics like a mother to her child. 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 appears to have noticed Yukino's similarities and feelings to her brother and has slyly set up a date-like situations between her and Hachiman. Yukino along with Yui and Hachiman selected Christmas present for Komachi. There are a lot of outings to which Yukino personally invites Komachi and the latter tries to set her and Hachiman up.
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 relieved after the misunderstanding were cleared.
She showed hints of jealousy towards Iroha's closeness with Hachiman, as seen 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 a relying underclassman and helps her in many ways and most situations.