Ki ni Naru Kanojo no Mama wa Gen'eki Mahou Shoujo - Shiborare Sandwich Seikatsu

Aside from his unusual ability to see things not of this world, Sumiyoshi Dai is an ordinary student. Lately, however, he finds himself drawn to his classmate, Hougetsu Aqua. One day, he goes to her house to hang out. There, he meets Aqua's mother, Hougetsu Ruby. Through an unexpected turn of events, he learns that Ruby is an active mahou shoujo - and soon, he's swept up in a series of mysterious incidents. Before long, he ends up providing Ruby with his semen as a source of magical energy, and the two gradually deepen their relationship. With Ruby's daughter Aqua, a mysterious woman named Kagami, and a girl named Dia who claims to be Ruby's mentor all drawn into the mix, a string of strange, sex-filled days begins. [Translated from the official website]