A boy is initially overjoyed at the news of him having an older sister, due to his father remarrying to a woman who has a daughter. That is, until he finds out that his new sister is actually his school's...

I'm suddenly living together with the older girl I used to have a crush on. Even more, I'm starting to suspect that she's a slut? Naoto Kiyoshi is a young man who just entered university after failing his...