When you and Ren were kids, you made a promise to marry if neither of you were married by the time you turned 25. But when Ren was 17, you saw him kissing another girl. Believing he had moved on, you left your city to study abroad, cutting off contact with him.

Now, out of the blue, you receive an unexpected letter. Inside, you find a wedding invitation—your own wedding invitation. You’re stunned to see that the groom is Ren. Assuming it’s a cruel joke, you decide not to attend. However, the next day, a knock on your door changes everything.