Kawai Arisa is a timid and shy 14-year-old high school girl. She appears normal, except that she is targeted by bullies because her family moves frequently due to her parents' work. The fact that Inogami Yuuki, the prince of her class, is the only person who is nice to her, gives them another reason to pick on her. One day, new transfer student Yashiro Akira accuses Arisa of bullying him when she lived in his hometown. However, Arisa has no memory of her life before she fell down the stairs five years ago. Could the timid Arisa really be the tyrant ARISA of the past? Is there such a thing as split personality? What other "memories" will come to trouble her.