Depending on the erotic game by Syrup: Honey Sweet.
Segawa Akira is often a high school graduation student who is one day caught masturbating by his older sister, Yuu, who then proceeds to help you him to help remedy his needs. Later tomorrow, Akira predicts Yuu, prompting her to determine to refer to him having a physician, Tachibana Kimiko. Kimiko explains that Akira has an illness that can simply be cured insurance firms sex with him. Thus starts the newest sex-filled life of Akira with his sister, doctor, and childhood friend Takamori Sana.
