Yea I agree it works out well in the end but out poor protagonist has to deal with it for a while. He loves her after all and he will always know that she did what she's currently doing.
This is a very old comment but I'm going necrocomment it anyway and say this book isn't a NTR. Yua was Haruya's old childhood crush but that's it. They aren't or were never in a relationship. She just has a pact to bang her tenants. He'll just have to live with it.
Hentai related to Welcome to Tokoharu Apartments - Chapter 1