I can't tell my wife... We met my beloved cousin Tsubasa-san for the first time in 10 years on our return home. Three days of immorality, when two people, first love and married, lost time and fell in love.

At the end of the year, I returned to my parents' house, Niigata. There they met their cousin Tsubasa-nee for the first time in 10 years. The sweet and sour memories of those days are brought back to life as we meet again for the first time in a long time. After all, she is my first love and my first kiss. "Hajime-chan...I've become a married woman." But she has a husband... And I have a wife... Even if they are first in love, they are married. There must never be a mistake. I never thought I'd spend three days going home with her and spending one night under the same roof...