美少女万華鏡 -罪と罰の少女-

Yuuma was forced to take a hiatus from school due to unspecified circumstances that left him hospitalized.

After a year apart, he finally reunites with Yuuri, his breathtakingly beautiful twin sister, and they start living together. Nonetheless, Yuuma harbors a secret that he can never share with her - he's head over heels for his own sister...

As the truth inevitably comes to light, the love becomes an obsession that threatens to swallow him whole...

[Translated and edited from the official site]