Kotaro Yanagisawa

Shiro is a mysterious man and former caretaker of Itona Horibe.

Personality
During his first appearance, he seems almost funny and easygoing, but as he continues to manipulate Itona into attacking Korosensei, his true colors were revealed to be much more conniving and manipulative.

Trivia

 * His clothing has shown to be of the same material that the 'Anti-Sensei' weapons are made from, as Kurosensei was unable to touch him without the offending area being destroyed.
 * He has been shown to have a device which emits a beam of light that paralyses Kurosensei for a short period of time. Whether this works of Itona is unknown.