|Surname Name||Yamaguchi Yumi|
|Birthday (Age)||October 31st (n/a)|
|Type of Character||Main Cast|
|Height||5′ 6′′ (166cm)|
|Job(s)||Selling stolen candy and TVs|
'The class delinquent. Yumi doesn't particularly seem show to any interest in the other girls other than picking fights with them.[...] I used to see her hanging out at a local arcade with a bunch of Yakuza-looking guys[...].'— Sensei's notes
Yumi alternates between living in a room in the dorms with Chika and at Chika's home in the old district where she helps to take care of Chinami. She wanders the city in her free time and is particularly fond of a bridge overlooking a street. Sensei often finds her here.
Yumi is the class troublemaker and frequently skips school. When she does attend, she spends most of her time berating Sensei and the other girls, especially Futaba. Sensei eventually learns that Yumi's father is a Yakuza affiliate and her mother, Yuki, is a recovering addict who abandoned her at a young age. She makes some money selling stolen candy and televisions, but ultimately relies on Chika and eventually Sensei to support her. The only ones she tries to act responsible around are Chika and Chinami. Despite her anti-social, willful personality, Yumi has difficulty achieving financial or emotional independence from the small support network she has been able to maintain.
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.
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. Yumi seems to genuinely care for Chika and doesn't want her getting used by Sensei. They bond over taking care of Chinami Chosokabe.
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.
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.
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 clothes and living a similar lifestyle. Yumi was not aware about her living in Kumon-Mi until accidentally meeting her at Tojo Ramen.
Little is said about Yumi's father other than that he is a Yakuza affiliate and that he is no longer present in her life. Both she and Yuki hold him in very low esteem, and she expressly mentions trying to live differently than he does. Despite that, she would spend time around Yakuza members before the events of the game, likely associates of his.
"Not like I have anything goin' for me. Fail at shit all the time. Succeed at shit never." -Abyss
"Fuck you." -All the time
- Yumi's Birthday is mentioned in Guest of Honor by Chika.
- 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.