Yeah, when I think of a Win-win relationship, I think of a Vanilla filled relationship with a tsundere.
Still...'Go back to how things were', eh? Well, not if our protagonist has something to say about it. Good on him though for not backing down and just keep going for it.
And he got himself a girlfriend for that effort. Great ending.
Dating would be a win-win? Yeah, I'd say so. Considering she seems pretty close to his parents, they probably already consider her their daughter or something...So it's probably only a matter of time before she officially does.