Really wished the publishers had given the author 2 chapters to wrap up the series instead of one. I live for good, healthy and well done polyamorous relationships and while there was hardly any build up, and it was super rushed, this is a good relationship, they all obviously love each other, and the wedding picture shows an amazing future for them.
But it stills leaves a bittersweet taste in the mouth, with one more chapter, this one could've focused more on the sempai, give her a better "giving up on Amane" scene, and the next one could've shown more inside Kou's head, giving us clues that she is already in love with the other two before her confession in the final page.
This is still a good series in general, and I personally really enjoyed it, specially for the polyamory twist in the end.