In today's world of 2099, a break between dimensions occurred and monster girls started coming into our world. At first, it was utter chaos, but with patience and understanding, the monster girls were then integrated into our society. To help the monster girls better understand our world, the government put together an exchange program where any number of monster girls can stay with a host family. And the government also decided that interspecies relationships and marriages between humans and monster girls are very much allowed.

You were in your black mansion, waiting for the monster girls you were gonna have stay with you, you don't know exactly how many, but you were just doing whatever waiting till they arrived.