Haruno & her friends shown during Hachiman and Yukino's shopping
Haruno seems to hangout in groups of both genders but Hachiman feels that she doesn't establish any equal standing relationship with anyone. Haruno seems to be liked and respected by all who have met her.
Family
Father
Haruno's father is a member of Chiba's diet and also the CEO of a construction company. She sometimes acts as her father's representative in public events. Her father seems to be more lenient than her mother. Haruno describes her father to be a good cop while her mother plays the bad cop in dealing with their children.
Mrs. Yukinoshita (Mother)
Voiced : Kikuko Inoue
Mrs. Yukinoshita
Her mother was introduced in season 2, Episode 10 (adapted from Light novel Volume 10, Chapter 2), where she came to meet Haruno, Hayato and Yukino to their family holiday dinner. Haruno mentions in Episode 9 that her mother is much scarier than herself and makes all the decisions for the family which they all had to compromise.
It was her decision for Haruno to represent her father and for Yukino to stay in the shadows as a substitute for Haruno. In Season 2, Episode 11 (Adaptation of Volume 11) Haruno was ordered by her mother to stay at Yukino's house.
Yukino Yukinoshita
Haruno teasing Hachiman and Yukino as a couple
She is the younger sister of Haruno. While Yukino holds strong animosity towards her, Haruno sees her sister who's constantly trying to overtake her as cute. She often meddles in Yukino's life, in either to help her grow or get something she wants. She enjoys poking fun at Yukino and even goes to the extent of using sarcasm and "sweet" behavior to go aggravate her. Yukino plainly resents her for her ways even though she admits that Haruno is a "perfect woman".
However, Haruno cares about Yukino in her own way. Despite putting on a cold face in front of Yukino, she sometimes almost breaks to the point where she shows that she is actually regretful for making things end up in a way where Yukino thinks of her as someone who poses a challenge to her own life. But their relationships in the past,before the start of the series are yet to be revealed.
They have contrasting names, Haru means spring and is associated with warmth. While Yuki means snow.
Family friends
Being the eldest child of the Yukinoshita's, she was taken around for work related courtesy visits or parties. Making a lot of acquaintances during this time.
Hayama family
Hayato family has a business related relationship with Yukinoshita. As result Haruno developed a decent relationship with them. According to Haruno, Hayato's parents were affectionate with her and Yukino, almost like family. Yukino doesn't quite agree.
Hayato Hayama
He is the childhood & family friend of Haruno. Haruno tells Hachiman that Haayato was more like her brother. Haruno has a familiar relationship with him, as they both call each other by their first name. It was mentioned in the light novel that they know each others true personality. It is also mentioned that both Hayama and Yukino look up to her. Once Hayato acted coldly for dragging him to a date with Kaori. Full details of their relationship are yet to revealed.
Soubu High School
She is an alumnae of the school and has made a lot of acquaintances in the school and also it's alumni. She often visits for various reasons. She volunteered for the Culture Festival on her own motives or from persuasion by Shiromeguri and performed with her musical orchestra.
Shizuka Hiratsuka
Shizuka and Haruno in cultural committee
Haruno is the former student of Shizuka. They seem to be on good terms. Shizuka knows about Haruno's true personality but doesn't seem to bothered about it. She describes Haruno as a good student, free willed, and easily likeable.
Even though they have a teacher-student relationship, they call each other by their first name. Haruno can see the kind-hearted motherly nature of Shizuka and can predict her motives, as she was able to see the reason behind Hachiman's participation in Cultural committee. Once Haruno invited Shizuka for a drink and pointed to Hachiman that they used to have one since her graduation.
Meguri Shiromeguri
Meguri recommend Haruno to Yukino
Haruno is her former upperclassman whom Meguri greatly admires. She played in a band along with her as well. They seem to be on good terms with each other. It also seems they are on regular contact with each other, as Meguri invited Haruno for the Cultural Festival committee.
Hachiman Hikigaya
Haruno teasing Hachiman
According to Hayama's observation, Haruno seems to be fond of him, as she always meddles with him. She seems to like pairing up Hachiman and Yukino even trying to get Yui Yuigahama to back off, suggesting she believes they would make a good couple, with them denying such a possibility. She constantly addresses Hachiman as her future "brother-in-law", to the annoyance of the latter. For that reason, she tries to get him to call her "big sis" only for him to call her by her last name as she notes he is stubborn.
Hachiman is one of the few people to see through her façade. She acknowledges Hachiman's perceptiveness and often playfully teases him. While Hachiman is put off by her since he doesn't know much about her. In her eyes, Hachiman is the first male outside her family circle to get close to Yukino. Hachiman compares her to his own sister in regards to her meddling behavior but does nothing to stop her since she is looking out for her sister.
It is not clear whether Haruno is truly supporting the budding relationship of her sister or doing it for fun. But there are instance of her getting cold to Yui for getting close to Hachiman instead of Yukino .
It was later revealed that she also knows about the car accident that involved Hachiman, Yui, and Yukino. She lets this slip as she thought Yukino told Hachiman though she quickly excuses her sister from any wrong doing but Hachiman tells her it was alright. After the Culture Festival, she congratulated Hachiman for his bravery during the confrontation with Sagami, and admired him for it. Haruno calls Hachiman a "Monster Of Logic" because of his critical analyzing of people's behavior.
Haruno also sets-up Hachiman and Hayato on a double date with Kaori Orimoto and her friend. For her to know of Hayato's intention of involving Hachiman and also because of seeing things to be amusing.
Yui Yuigahama
Haruno's first impression of Yui is very demeaning, as Haruno warned while smiling that Yui should stay away from Hachiman, as he belongs to Yukino alone.
Haruno, Hachiman, and Yui at the Fireworks Festival.
The second time they met was at the Fireworks Festival. After hearing that Yui is Yukino's best friend, Haruno advises her not to leave Yukino like her previous peers, to which Yui replies seriously that she won't abandon Yukino and loves her as a friend.
Haruno also expresses her concern that if Hachiman were to choose Yui, Yukino would "lose out" again, not explaining properly.
Iroha Isshiki
Iroha made her acquaintance during the pre-valentines day event (in the anime). Iroha tried to appeal to Haruno which Haruno sees through.
Others
Komachi Hikigaya
Shown neither on-screen nor in the light novel, it was mentioned they sometimes meet or exchange messages. It was shown that they exchanged contacts with each other as a way for Haruno to keep in touch with Hachiman. It was also mentioned in the light novel that they exchanged their contacts during the Cultural Festival of Soubu High. Haruno also wishes to have Komachi as her sister. Both of them seem enjoy pressuring their siblings into relationships.
The only time they were shown together was during the time the Service Club members returned from the Chiba village, where Haruno was waiting to take Yukino home to their mom in Episode 8 of Season 1.
Kaori Orimoto and Chika Nakamachi
Haruno meets Kaori for the first time.
Haruno made their acquaintance at a cafe with Hachiman. Kaori misunderstood Haruno to be Hachiman's girlfriend but after realizing the truth, Kaori stated her opinion that Haruno is out of Hachiman's league.
Haruno also learned about Hachiman's past and confession to Kaori from her. Haruno also introduced Hayato to the girls. She indirectly set the stage for the double date and followed them without their knowledge throughout their date, as she felt that things were amusing. Haruno also wondered about Yukino's reaction, if she learned about Hachiman's confession to Kaori.
Not much interaction evolved between them after the date, even though Both Kaori and Haruno were present at the Pre-valentine event, it may be due to awkwardness in Kaori part to approach Hayato's acquaintance while Haruno may have lost interest in Kaori and ignored her.
However when Kaori promise to give valentine obligatory chocolate for Hachiman, it triggered a set of reaction from their peers which attracted Haruno's interest and she sets off another triggering information.