Lilythtia International School is located in Mitsuoka-chou where Kento lives, attracting many students from overseas. He helped out every day at his father’s flower shop Florist Ogiwara in the shopping area with the intention of carrying on the family business in the future. One day while he was on an errand, he was assaulted by a beautiful girl who he had seen at the school before. When he woke up in the hospital afterwards, her servant Riel told him that she was Runastia, a succubus ‘princess’ who has a weak body. She asked him for help since his life force was special and it may be able to cure Runa. After giving it some thought, he decided to transfer to Liliythtia, which was actually a school for succubi. Surrounded by ero classmates, will he be able to graduate from the school without being sucked dry?