ボクの貞操を奪わないでっ!!

The main character has been studying hard for three years to enter medical college. One day, his cousin starts living at his house to go to school nearby. Though he only slightly remembers her, he is excited to hear that. On her first day at his house.... She is quiet in front of his parents, but she soon behaves selfishly in front of him. When he is at a loss what to do, she just whispers in his ear, "Long time no see..., Shiro...." "What!?" Like this, his tragic (?) life starts....