Modern-day.

Yuki Tada is an office worker. Although he is not married, he has a carefree life with an understanding boss, dependable friends, and cute junior staff members. However, he has one regret. He did not confess his love to the girl he liked when he was a student. One day (Christmas Eve), the protagonist comes home from work and notices a postcard. It was an invitation to the wedding of the girl he used to like.

That night, Yuki falls asleep alone and thinks, "I wish I could go back to that time and do it again", he wants to live his life with the girl he loves.

Then Santa (the heroine) appears to Yuki. To Yuki's surprise, the heroine sends him back in time to make his wish come true.....