Birthday: April 16
Blood type: A
Hayasaka is a delinquent and a classmate of Mafuyu. After a series of events Mafuyu declares Hayasaka her best friend, although he's actually deathly afraid of her at first because of the dark aura she emanates during class. Later he and Mafuyu are forcefully recruited into the disciplinary club by Takaomi.
As he is called only by his surname his first name remains unknown, it is one of the mysteries that revolve around him. In the first volume chapter five Mafuyu asks him why he didn't have his first name written in his textbook but he answers that his class and last name were enough.