|Surname Name||Yamaguchi Yumi|
|Birthday (Age)||October 31st (n/a)|
|Type of Character||Main Cast|
|Eye Color||Dark Purple|
|Height||5′ 6′′ (166cm)|
|Job(s)||Selling stolen candy and TVs|
'Yumi is the obligatory class delinquent. She doesn’t particularly seem to show any interest in associating with other girls apart from picking fights with them on a near daily basis. The only one who seems to be an exception to that is Chika. […] Her attitude is getting worse every day and even calling her into my office doesn’t seem to work anymore.'— Sensei's notes
Yumi Yamaguchi ("Yumi") is part of the Main Cast of Lessons In Love. She is part of the original ten girls in Sensei's class. She lives in room 1 with Chika Chosokabe.
Yumi was born as the daughter of Yuki and the unnamed head of the Yamaguchi clan. Due to her father not caring about her and her mother being high most of the time before abandoning her completely, Yumi was forced to rely on herself early on. One of her few friends was her older cousin Kaori, who visited her until she was severely injured in an accident and hospitalized. After not receiving any new information about her condition for a long time, she assumed that she didn’t make it.
At some point, she became fed up with her family and the yakuza life, leaving the estate behind. She later met and became friends with Chika and her little sister, Chinami. She enrolled into Kumon-Mi High, though rarely attends class.
Yumi acts like what someone would expect from a delinquent. She’s rude, vulgar, short-tempered, acts disrespectful towards anyone, except Chika and Chinami, enjoys belittling those who are weaker than her, which is usually Futaba, frequently skips school, commits petty crimes, and spends most of her time alone.
While some of these qualities, especially her behavior, haven’t change much, she starts to improve her life and grows as a person as time goes on and due to Sensei’s influence. She genuinely tries to get a part-time job, picks on others less and less, even apologizing to Futaba for bullying her, gets calmer and more approachable in general interactions, though her short temper still persists and she can easily snap if someone hits a nerve, and becomes a little more social as she joins a club and seems to participate in regular club activities.
Despite her usual behavior, Yumi can behave herself, though that mostly happens during her interactions with Chika and when she is around Chinami.
Yumi has a strained relationship with Sensei dating to before his current incarnation. She says that he used to track her down in the arcades and that he constantly gave her detention. She is, however, one of the first to notice his change in personality and is bothered by the inconsistency. She thinks lowly of him due to his relationship with the other students, referring to him as "a fucking creep who spends too much time around teenage girls", and entertains no delusions about his moral fiber.
While she has an overall negative opinion of him, Yumi doesn’t hate Sensei and appreciates his attempts at helping her with job hunting, admitting that he's done more for her than every other adult. After Nodoka’s blackmailing, her feelings about him before more complicated. Between everything that he did for her until then, his passiveness during the incident and his rant at the end of the second Dorm War, she’s left in a state of total confusion and uncertainty where she can’t figure out if she hates him or not.
Despite her attitude towards him, there are a few people who think that she likes him. Chinami is one of those as seen in The Gap in the Door and even Nodoka assumes that she starts to fall for him, which is one reason why she used him in her revenge plot.
Chika is Yumi's best and only real friend. She seems to be the only one who can calm Yumi down or get her to cooperate, though even this has limits. Yumi seems to genuinely care for Chika and doesn't want her getting used by Sensei. She also helps her by taking care of Chinami when Chika needs to leave for work.
After what she did to Nodoka, she feared that she destroyed her only friendship, which was the reason she went back to her father’s estate rather then going to her when she couldn’t handle life on the street. When Chika assured her that this alone isn’t enough to negatively impact her opinion of her in a significant way when she tried to get her back, Yumi decided to move into her flat again so she can be her full-time babysitter for Chinami and get away from her home once more.
According to Chika, Chinami is the only one to know "the real Yumi", as she brings out a warm, protective side of her that no one else does. Yumi takes care of her together with Chika; however, she has evidently missed out on babysitting several times in the past despite promising to do it while Chika is working and has accidentally given her peanuts despite her allergies, though that was partly Chinami’s fault as she didn’t tell her and ate them anyway.
Yumi constantly belittles Futaba for her weight and goes out of her way to pick on her, causing friction between her and virtually everyone else in the class. She shows little remorse about the fact when confronted by Sensei. It is implied she bullies her because Futaba won't stand up for herself and this bothers Yumi for personal reasons.
As time goes on, Yumi bullies her less and less until she finally apologized to her in See You Around and promised to not pick on her again. Yumi hasn’t interacted directly with her since then, because while she has no intention to belittle her anymore, she also has no reason or interest in befriending her.
Yumi holds considerable anger for her mother on account of her neglecting and eventually deserting her as a child, a fact that both of them attribute to Yuki's drug abuse. She seems to express no interest in a relationship with her mother despite wearing her skirt and living a similar lifestyle. Yumi was not aware about her living in Kumon-mi until accidentally meeting her at Tojo Ramen.
Since then, they only had two meaningful interactions, one being their meeting in a convenience store, where Yumi vented her frustrations and yelled at her for her past behavior until Yuki shut her up when she acted disrespectful towards Sensei, and when Yuki visited the estate to talk with her, which was the first civilized conversation they had after a long while.
Little is said about Yumi's father other than that he is the head of the Yamaguchi clan and that she does her best to avoid him. Both she and Yuki hold him in very low esteem, and she expressly mentions trying to live differently than he does. Despite that, she still returned to him after her suspension and lived in the estate for a while, even considering to drop out of school and return to him completely until she figured out what to do with her life.
- "Not like I have anything goin' for me. Fail at shit all the time. Succeed at shit never."
- "Apologizing to people is fucking exhausting."
- Due to her father being the head of Yamaguchi clan, the members of the clan refer to her as 'princess'.
- Yumi shares a birthday with Selebus' father.
- Yumi was the winner of the second Lessons in Love Gravure Poll, for the month of June 2020.