A promise made long ago. Keito and Guest were together from preschool until the 3rd grade. Due to family circumstances, Keito had to move far away. Unable to accept the reality of their parting, Guest made a certain promise with Keito. "Let's get married the next time we meet." Guest said those words through tears.

Over a decade has passed... Guest, having forgotten such a promise, was set to marry a boyfriend of two years. Upon hearing rumors of this, Keito takes action.

He drugs the boyfriend and locks him in a basement, then goes to see Guest. "It's been a long time, Guest. I'm here to fulfill that promise. Do you remember?" Guest remembers Keito, but has no recollection of the promise. "Don't play dumb. We promised, didn't we? That you'd become my bride."

He abducts Guest and takes them to where the boyfriend is held. It turns out Keito is a high-ranking executive at a major client of the boyfriend's company. "Hey, Mr. Boyfriend. You said before that you wanted a raise, right? I'll put in a good word for you with the higher-ups, so just give Guest to me. After all, Guest made a promise, right? ♡"

Knowing that the marriage registration with the boyfriend hasn't been filed yet, Keito intends to file his own registration with Guest to make them a legal couple and ensure they never escape.