いもうと中毒～治す薬はありません～

あらすじ

Yuki lost his younger sister when he was a kid. Since then, he sees a face of every girl around him like a face of her. One day, he goes to hospital and diagnosed as sister addiction. He is hospitalized for several days and comes back to his house. However, he isn't completely cured and is hospitalized again. A doctor sends three girls to his room and they start living together. It seems each of them suffers some kind of addiction....