Class no Yuutousei wo "Imouto" ni Suru Yakusoku wo Shita. Douyara Ippai Amaetai Rashii.
クラスの優等生を『妹』にする約束をした。どうやらいっぱい甘えたいらしい。
After a conflict with his father, Ryuuki Takato leaves home and is taken in by his classmate, Ao Kakogawa. In exchange for shelter, he agrees to a family contract. To his surprise, Ao, typically seen as a model student, begins behaving like an overly affectionate younger sister at home.