- "There's no need to hurry, I'll die one day, anyway...Anything that's living will die one day, so it's better to live happy and make others happy whenever we can."
- ―Yoichi, to Desir[src]
|First Appearance||Chapter 2|
|Team||The Good Dôji Club|
Yoichi Oizumi (大泉 洋一 Ōizumi Yōichi) is a 42-year-old business manager and the master of Service, one of the "Six Perfections".
For his age, he is a relatively short and thin with squinty eyes, making them appears close. His facial features comprise of light colored medium length hair. As he is a business man, he wears a light-colored suit and carries around a black suitcase with him.
In his first few appearances, he was shown with some aged wrinkles and with a more squat figure, causing him to look hunched over. However, starting in Chapter 21, he becomes leaner and taller, appearing much more confident and younger.
In Act 44, it shows that Yoichi's ICON suit is similar to a 1900s styled male swimsuit, mostly light-colored with dark stripes and two wrist cuffs.
He is a very quite, modest, and well-mannered man, who always wears a calm smile on his face. As noted by Service, he holds a great love for everybody, and that while doing so he never complaining about his own situation. Rune Kodaira cites his harsh family life and the fact that he often let himself to push around by others gave him a tough yet gentle spirit.
Yoichi is very philosophic, having a deep understanding of how human nature and moral values often clash together in complicated ways and tries to see the best in everybody. Therefore, he holds a moral relativism mindset that allows him to be thoughtful, open-minded, and sympathetic to others. After most of his comrades had died or retired, Yoichi become the only adult within the The Good Dôji Club and acts as the source of wisdom and comfort for the younger members. He even took over Shin Ekoda's role as a mentor figure to Yamato Agari and give advice to Musashi Murayama when needed.
Service is his dôji and they are very close, and he has even said that Service being with him is one of the reasons why he can smile everyday. His love for Service is so strong that it can quickly heal him when hit with an attack and let Service recharges his energy fast so he can use powerful moves.
- (To Musashi) "Pain and sadness are tests from God. If we panic, if we give in, that the worst form of failing! We must always be good."
- (To Yamato) "There is neither good nor evil. I agree with you whole-heartedly. Good and evil are different for each person. And one person may do a 180-degree turn depending on the situation. So here's what I think...Everyone is merely struggling to survive."
- (To Service) "I'm not surprised. After all, anger is a just response to injustice. Fussa Fusataro's rage...is born of his love for music."
- In Chapter 23, it was revealed that he has a wife and a 28-year-old son, but he's isn't very close to them.
- He can be observed in one of the earlier chapters as just an innocent bystander, within a large crowd during the bus incident.
|The Good Dôji Club:||Yamato Agari · Shin Ekoda · Yoichi Oizumi · Koun Shakujii · Musashi Murayama · Hiroshi Kumegawa · Machi Shina · Makoto Sayama · Akitsu Otake · Hibari Oume · Kiyose Matsumoto|
|Allies:||Darumada Masami · Hyoe Tokorozawa|
|The Evil Dôji Branch:||K · Akira Hidaka · Kaizo Oume · Fusataro Fussa · Sumako Miyoshi · Mizho · Rune Kodaira · Hana Koganei · Tomomitsu Iruma|
|Unspecified/Neutral:||Roger Dunstan · Miyu Murayama · Taiji Kokubun · Fushimi Agari · Yuu Ekoda · Shinsaku Ekoda · Saishinsaku Ekoda · K's Grandmother|