Mami Suzuki

Mami is one of Sana's friends. She is a quiet girl, with short black hair kept back by a hairband. During Akito's troublemaker days, she calls Akito a "monster," "demon," or "devil" (depends on the language), which is a particularly hurtful word for Akito to hear since it's what his sister calls him. Akito gets revenge by getting the other boys to throw Mami into a pond, which causes Sana to become angrier than she's ever been. Mami remains traumatized by this incident for quite a while afterwards. She remains so afraid of Akito that when he tries to talk to her, she screams and cries. But when she sees that Akito regrets the way he's acted in the past, they reach an understanding.

(Source: Wikipedia)