Manga hunt pls help

The story is a bl very similar to Hime Muko, but they both die in the end. I think the story was a one shot with one or two chapters for most part not in color. These two boys live in a village that is closed off from the rest of the world due to monsters roaming around outside of it. The village is gated off with red rope and they are aware that there are other villages who are also isolated from the world but have never seen or visited them because they deem crossing the rope as too dangerous. One of the boys is like an orphan with long white hair and as they get older the orphan boy is subjected to be god’s bride which is just him sitting in a dark cave abyss surrounded in red rope (this is like a scene that everyone had in one of their albums because the image is beautiful yet haunting). This ritual is a tradition so the god can continue protecting the village and prevent them from becoming demons, however no one in the village including the boys have ever seen a monster. So the other boy grows up to be a warrior so he can someday save his childhood friend and leave the village together.
The warrior boy sneaks into the shrine like abyss to basically steal god’s bride, and rebel against this tradition which ofc entails them having sex on the giant bed in the shrine room, because apart of this ritual is keeping the boy pure for the god. Throughout this story the belief in god and demons being real is kept very ambiguous. So the twist is when they finally leave the shrine they realize that the god and stories about monsters were real because everyone in the village has turned into a demon. The warrior boy also turns into a whale like monster with no face and the god’s orphan bride reaches out to his once human lover to accept his fate and be eaten by him.
What made the bleak ending even more tragic was before they found out that their god and monsters were real they both came to an agreement that being consumed by monsters or becoming them would be better than life trapped within the village’s rope barrier as long as they’re together, so the really sad part is that they had so little time together and when everything was said and done they didn’t turn into demons or die by them together only of them turned and the other had to get eaten by him. Im willing to include a crude drawing of what the warrior boy turns into if that helps.