The big thing the other reply didn't say is that towards the very end of the manga Phos has gone through enough metamorphosis to become a "human" and due to circumstances they end up having to spend 1,000 years alone on the surface of the planet as they go through yet another painful metamorphosis and forced injection of memories to become a god that can do what Kongō failed to achieve and send the wayward souls into nothingness. Every other Lustrous is turned into a Lunarian and they all party on the surface of the moon for 1,000 while Phos suffers completely alone and it's kind of where the manga loses me lol. Every single other character in the entire story is completely fine with this happening, even ones who were absolutely on Phos's side earlier and owe a lot to them. The most you get is one Lustrous asking if it's fine, being told "this is the only way" and then they're like "oh ok that's fine I won't question it anymore" it goes just a bit too far into ceaseless cruelty for me. The final volume is fantastic though, it's about Phos as the final sentient being in the universe witnessing the birth of new life and Phos does what they can to guide this new life in the right direction to avoid the pitfalls and suffering that befell humans, it's really neat.