Animated Tube - Dekakute Ecchi na Ore no Ane 01

Marine's erotica game served as inspiration. Shunsuke goes home to his family at the request of his elder sisters after a lengthy away. He discovers that his sisters are suffering from a unique disorder, in which they have unusually intense sexual cravings as a consequence of a sickness they contracted as children. In order to enhance their health, Shunsuke must now do all in his power.