Youko, a beautiful high school girl, has lived a mostly ordinary life. Like many others, she has gone through her fair share of hardships and worries, the most recent of these being the separation of her parents. Because of this, she lives with her father who is often away for work.

However, just as she has become accustomed to her new surroundings, she is visited by a strange yet cheerful girl who claims to be from the future. This time traveler—oblivious to the culture and technology of the 21st century—announces her one and only goal: to collect Youko's egg cells through sexual intercourse.