Boku wa imôto ni koi wo suru (2007)

Yori and his twin sister Iku used to be very close as children but lately he has grown colder toward her and is always eager to stay away from her. She was confused by his attitude. Actually he is in love with her and that forbidden love is causing him sleepless nights since they are sharing the same room with bunk beds. He tried to ease his intense desire for her by bedding her best friend. He had even applied to attend a boarding school in another city to take himself far away from her. He lost his resolve to stay quiet about his feelings when she started to talk about having a boyfriend and going on dates. Now he want to have his little sister and confessed. She loves her big brother and wanted them to stay together, so she is willing to anything to keep them together. But he wanted to have her as a lover, not as a sister loyal to her twin.