Tarowo Osanai has been dating Sayoko for three years. He proposes to her on her birthday, and they become happily engaged.

──But the afterglow of happiness is fleeting.

"Once you're married, you can't do anything! You should 'get your fill of fun' while you still can!"

Feeling a strange persuasiveness in his colleague's words, Tarowo ends up booking a delivery health service. There, he meets a prostitute named "Emiri." His dalliance with her will greatly shake Tarowo's fate──. Because "Emiri" is none other than Sayoko's mother, "Asako Kimura"......