Adult PC Game: Bishoujo Mangekyou -Tsumi to Batsu no Shoujo- by ωstar Archive

Yuuma is on leave from school since being hospitalized due to an incident.

For the first time in a year, he finally reunited with his beautiful twin sister Yuuri and began to live with her.

However, he had a secret that he could not tell the sister: he is genuinely in love with her.