The LN is ''Devil is a part Timer'' in which the Demon king (Maou) and the Hero (Emilia), after the Hero won the last battle, get isekai'd to Earth
and live normally so to say.
The author have been developing them together all the time, going over their reasons, their motivations, etc. They even 'adopted' a kid together
yet in the end
Chiho is Maou's normal Coworker who always had a crush on him, but it was always one-sided.
And that last line is really cringe
Enjoy 😄