A single mother named Nina has raised her son alone. When he got a job and encouraged him to move out, he refused. She decided to take him on a hot spring trip to convince him. During their vacation, her son suddenly confessed that he had always liked her more than his girlfriends... ever since they were little. As she listened to his longtime feelings, she gradually became serious about him. Seeing her son feeling bad because of her, she thought she was just showing some maternal love... but it turned out to be more intense than expected. They made a promise to do it once, but couldn't resist each other's passionate desires. This taboo story tells of a mother and son who continue to mate despite their initial agreement.

女手一つ息子を育ててきたニーナ。息子も就職し一人暮らしを勧めたが出ようとしない。たまにはと温泉旅行に誘う。旅行先で突然の告白…彼女も居なくずっと母が好きだったと言う息子。小さな時からの想いをぶつける息子に徐々に本気になっていく母。私のせいで童貞の息子が不憫に思えて…ちょっとした母性愛のつもりだった…。一度だけの約束だったが、激しい快感に喘ぎ感じてゆく母。何度も交わってゆく禁断の母子相姦物語。