Arisa - Manga

For years the rash tomboyish Tsubasa had communicated with her twin through letters. She had formed the idea that the gentle Arisa led a joyful school life. But upon Arisa's sudden suicide attempt, Tsubasa vows to find the reason behind her twin's actions by taking her place at school. But will this supposed joyful life be too much for Tsubasa to handle? What does it have to do with the people disappearing from Arisa's school...