In a world where the number of women being born is decreasing and it's now mainly a male society. The scientists are trying to figure out a way to bring back humanity and fix this virus. One of the famous, upper class, bright, young, and handsome scientists named Mikoshiba has come to the lower class area in order to help their research due to his interest in a cute, naive but average scientist named Niino who dreams of saving the world. Mikoshiba now moved in with Niino, has a theory in which he wishes to try out. His theory is that by them having sex and sexual relations that they might be able to solve the world's problem!

Note:
- Includes the side story "Koibito Gokko-hen (恋人ごっこ編)"; Libre Premium 2012: Diamond Gold
- Includes the extra "Sono Yoru no Ohanashi (その夜のお話)"