After his apartment was burnt down to ash, Koide Yuu got to stay in a high class mansion because of his wealthy friend’s help. However, the situation changed drastically when his friend’s brother, Oosawa Masakuni suddenly appeared at the mansion. And then the days Yuu became Masakuni’s guinea pig for his sex experiments (which he had no choice but to agree in order to pay for the rent and compensation for an antique vase he broke) began! (from Shinmakoku Scanlations)