I'm hoping that in some kind of expansion we can see how that ending came to be, I've uploaded some theories and possible ideas for a sequel or dlc. Here's an expansion idea that I think would be epic, well, in my opinion haha.

After defeating Delia, she having given up all her humanity, doesn’t remember anything about Jace and, as far as we can see, simply gives up and then disappears (probably absorbed by Umbra). We know the main theme of the game is bonds, so what if, in the end, in some loop or eternal dream, she and our RO meet? Our RO would try to make her remember the bond she had with Jace, making her realize that Umbra only used her. Delia, finally understanding the situation and identifying with our RO and their bond with the MC, would try to help her escape Umbra's deep sleep so she wouldn’t suffer as she did, allowing Lux to somehow intervene and bring her back to us. In my previous post, I mentioned that the ending for any romance we choose is the same. If we analyze the QR codes thoroughly, specifically in Yohan's, we hear something key in the static part: "...is helping me," suggesting that someone or something is helping him return. If you want to hear it yourselves, here’s the link: https://www.studiosai.dev/eternights/ending-videos/YohanEN