I have a younger sister who has been living separately since junior high school due to my parents' divorce. I live with my father and she lives with my mother. However, this summer, for some reason, my father suddenly said, "Let's rebuild our house!", and I... had to suddenly move in with my mother and my younger sister. I had only just met my sister this past New Year's, so there was no chance of an emotional reunion... or so I thought, but now that we're living together after such a long time, I'm strangely excited (sweats). And what's more, my mother will be away on a business trip during the time I'm staying with her... "So it's just me and my sister here for a summer?!" While I was having this thrilling fantasy, three unknown girls appeared in front of me??? "We're not the only two. I have friends coming to stay." "Oh, that's right..." I thought with relief... No!!!!!! My little sister, three strange girls, and me, all spending the summer together... under the same roof, here... Wait, isn't that more erotic?!!!!!!! An so an eventful erotic story starts without warning. What will happen next...? [Translated from Official Site]