Tomohiro, the protagonist, is an university student and a particular teacher. On his birthday, he receives a call from his older brother Tsukasa, a scientist.
Tsukasa says he can't visit him on his birthday so he has sent to him his present. And his present is... two cute girls!
These girls are actually replicants, live androids imitating real girls. And Tsukasa wants Tomohiro to secretly test them for a while.