This manga is SO FUCKING GOOD!!!!!!!!I can't believe people are bitching about the ending not being concrete when that is the EXACT POINT of the entire story. Did you troglodytes sleep through the many many explanations about how they'll continue in their dance of reincarnation full of familiar faces over and over and over again? The whole manga culminated into starting over again, and experiencing a new life to enjoy before once again repeating the cycle...
If you don't like that the author didn't show their relationship fully blossoming, you can 100% expect it to happen to one of the many reincarnations they've had since spascifica's blessing. Damn you "people" just can't be satisfied with an ending as meaningful as this.