|Family|| Unnamed husband|
|First Apperance||Chapter 72|
"Hiroki... mom have something to said... I was... a bit unusual... I... was feeling killing was so great...... even mom myself can't control at all... At that day... compared to my family's death impact... the killing feeling was way stronger... I was... I was really surprised...... Sorry... I'm so sorry... I'm very sorry... mom is such a person like this..."
– Kotoko Tobe when she is nearly die, Chapter 130
Kotoko Tobe (斗部 コトコ, Tobe Kotoko) is a character introduced in third part of the story. She is one of the antagonists in third part of the story.
Kotoko was lived in a small house with her husband and her son Hiroki and they were live in happiness. Until one day, an thief come into Kotoko's house and killed her husband and son. Kotoko taking her kitchen knife to defend herself and kill the thief. After Kotoko killed the thief, she feel an very great feeling on killing, so she changed her original lifestyle to killing people.
After that incident, Kotoko keep continuously killing innocent people non-stop. Until Kotoko is finally catch by the police and sent into the Jail.
Chapter 71- (Third Season)Edit
- Superhuman Speed - Kotoko can did a very fast moves with her attacks.
- Both Kotoko and Mizuki shared a lot of things similar. Both of them are living in their illusion world that need to killing people to achieve their goal. Both Kotoko and Mizuki's blood type is O.
- Kotoko's wish that want to be achieve by Marble is "Release from Jail".