Arisa and Mika, they are Nanase's sisters and school super-idols, they are hot and pretty school girls. Sousuke is a normal high school boy who, like all other boys, can only look at the super-idol sisters from afar. Sousuke loves Arisa, but can't even hope to talk to her. But one day Mika tells him that she wants to talk to him after school. After school, he meets Mika and Arisa, and they tell him that they are now his sisters! Sousuke's father, a real adventurer and the sisters' mother Nanase, an archaeologist met at a ruin dig in South America, fell in love and got married. Mika, Arisa, and Sousuke are now related and will live under the same roof from now on... Sousuke must be careful not to be caught by Mika or Arisa masturbating... Or who knows, maybe they'll give him a hand...? How about a bath with Mika...? Brothers and sisters sharing a bath together, after all...