Arisa

Tsubasa and Arisa are twin sisters who haven't seen each other for three years due to their parents' divorce. They have communicated through letters, but finally decide to meet each other again. Arisa, the more gentle of the twins, suggests that Tsubasa take her place at school for a day, just for fun. However, there are things about Arisa and her school that she hasn't mentioned to Tsubasa--dangerous things.
(Source: MU)