|“||When I see such unpolished diamonds...I can't help but want to smash them to pieces.||”|
–Takeru Midorimatsu, Volume 12, Chapter 1
Midorimatsu is described has having an older brother or kindly uncle face with a manner, voice, physical height, weight, and movement of an average Japanese person. He has no distinguishing features making him able to blend in.
Midorimatsu has a personality similar to Reki where he is indifferent, calm, expressionless, and lacks individuality. Also, when angered, his killing intent becomes known when he starts to become undetectable by others. However, he is still able to interact with regular school's headmasters in order to get students transferred out of Butei High and into their schools.
Midorimatsu has a dangerous ability through the use of psychological techniques where he can become undetectable to others.and not be remembered by them, except with only a memory that he is a man. This causes all enemies minds to be in disorder when trying to figure out his location leaving them openings for an attack.
Midorimatsu was introduced at the end of Volume 11, where he announced to Kinji Tohyama and Reki that they would be expelled from Butei High. He later explained that the purpose of expulsion would be in order to transfer them to East Ikekuburo High in secret. When Reki challenged Midorimatsu, he showed his abilities and prepared to attack them until Kinji stopped her and agreed to the terms of the transfer. Midorimatsu later ordered Kinji and Reki to hold on to their weapons and Butei licenses for awhile to avoid retaliation, treat the transfer as a long-term secret mission, put their affairs in order, and leave without a trace. In Volume 13, Chapter 1 Midorimatsu would allow Kinji and Reki to transfer back into Butei High after expecting they would not be able to live a normal ordinary life.