W Futanari Musume Kyousei Keikaku ~Tenkousei mo Jikkendai ni Shite Shimae!

The protagonist, Kagano, is a student who studies relentlessly every day with the goal of earning a doctorate in biology. With that as his sole focus, he made no friends and lived a life dedicated entirely to his studies—a school life that appeared somewhat lonely to those around him... or so it seemed. However, due to a drug he created himself, he has ended up living together with his female classmate, Miki Osawa, who has become a futanari because of it. Then, one day, a cute girl appeared before him and shouted: "That's why... I want you to use the drug you made to make my cock disappear! Please, make me a normal girl!" [MTL translation from the official site]