Tasuki Ouno loves gals very, very much. After confessing his feelings to his classmate Mimori Riona, a gal in his class and being rejected with flying colors, Tasuki got down on his knees and pleaded with her.

"Then let me ... at least ... have sex with you just once!"

"What, are you serious about that? Ha ha ha ... then."

As Riona leaves, Tasuki is stuck on his knees alone. It was Riona's sister, Azusa Mimori, a charismatic gal, who approached Tasuki.

"You're so funny, shall we do it once?"

Tasuki had no way of knowing that a dreamlike harem with beautiful gal sisters awaited him after this.