Thank you for this awesome kinetic novel that -- as I realized only after reading the analytical threads on steam -- truly is a piece of literature, not "just a story". I'm a bit ashamed that I didn't try to analyze it while reading.
Now I'm not even sure about whether the Luce ending is true or not. After Claire "went down the stairs and disappeared", the same view of her standing above him on the stairs and the sun rising behind her he had when they first met comes again and she asks him to stay with her. Would be "the good ending".
Or was he just breaking all chains in a literal way when he says farewell to everyone including Luce when he gives her the empty box, meaning the figurine has disappeared (reintegrated in his now healing personality) along with Claire. After all, when they are about to kiss the light goes dark and after it comes again he has disappeared. In that case, the final scene would once more just happen in his imagination. This would be a very sad ending indeed.
10/10 for everything - story, CG art, background art, music.
My waifu is Claire (if she existed), the one to go for irl clearly (pun intended) is Luce.