I found another anime doppelganger for Celestina other than Yu Mei Ren from FGO: Sakuya Kaguya from an anime called Shining Blade. I know nothing about it, but now I can collect more waifu merchandise.
Update: the anime is called "Shining Hearts" and the character looks different in the show, dressed like a pirate. The version I thought looked like Celestina was a "professor variant" which was made as a figurine but has nothing to do with the show or game. Disappointing.
@Tfmonkey she's not a loli (big boobs). And yes the world she's in is fairly dark.
She is a good asian waifu.
@Lorgar She looks like a loli based on her head-to-body ratio, but that may just be the art-style. Gives me Tim Burton vibes.