Yellow (right), Blue (left)
Haku is Shiro's cat that he is secretly taking care of. He's a gluttonous cat.
Haku is a large white cat with one blue eye (right) and one yellow eye (left). He wears a green tie around his neck and has a gold ear tag in his right ear with the number 89 printed on it.
- "Ha" in Haku's name means "eight" and "ku" means "nine" which is an allusion to his ear tags number.
- Haku could also mean white like his white fur.
|Main||Jyugo | Uno | Rock | Nico | Hajime Sugoroku|
|Inmates|| Tsukumo | Honey | Trois | Musashi | Liang | Upa | Qi | Fuji-san | Kusatsu | Enki Gokuu | |
Ruka Gojou | Hachiman
|Guards|| Seitarou Tanabata | Yamato Godai | Samon Gokuu | Kenshirou Yozakura | Kiji Mitsuba | Inori Hakkai | Damian | Mao Nimaijita | Nijimasu Nanairo | Tomato Ichijou | Hitoshi Sugoroku | Houzuki Sanzou | |
Daisen Rokuriki | Daisen Kokoriki | Daisen Youriki | Genrou Byakuya
|Nanba Staff||Momoko Hyakushiki | Mitsuru Hitokoe | Shiro | Okina Otogi | Kazari Otogi | KAGU-8|
|Antagonists||Man with the Scar | Elf|
|Other||Kuu | Haku | Yamatomaru | Hanzou Hattori | Noriko Sanzou | Hihi Gokuu | Inmate 610|