From what I saw of the spoilers. I think I’m okay with that ending. Sure, the boys deserve better and to have their own bodies. Also the girls to who love them, but I’m fine with them being merged since there was actually some level of consequences because of the war and the dark violent side of humanity. It’s bittersweet and more realistic than the usual truly, perfect, ending most animes go for.
I feel bad for Shun too considering how he fought to save Ruri, but again, more realistic in a way, that it’s not the happy ending everyone would have wanted.
Also, it is sad that Leo did not manage to save his daughter, but he did start this whole mess with to begin with and I think it is just fitting. Again, not the ending the characters would have wanted, but realistic and bittersweet aftermath of the war and consequences of humans desires and ideals anr overall dark side