A rogue-lite RPG where you plan your moves to conquer a dungeon by getting closer to the heroine, Monica, occasionally having sex with other women, and making sure your guild dues are paid.
Researcher Leo was told on his first day at the institute that he needed to look after some mysterious creature -- an innocent girl who fed on semen... There seemed to be more to the girl's secret than that, but no one wanted to reveal the maddening truth.
Yuuki woke up to find his body has shrunken. Places where he does not remember, and his vague memory. Then suddenly Succubus appears,and he gets his semen taken by her. He continues to solve various mysteries in order to take his original body size back.