I didn't see either girl named, so I'll just call them Angel and Devil. Even though I understood Devil used to be an angel before her rebellion. Perfect story for Pride Month! I loved how the tragic backstory was told gradually with a shared narration switching between Angel and Devil.
By far my favorite panel is the early plot twist scene with Angel holding back her tears after seeing Devil for the first time in a thousand years: https://e-hentai.org/s/9ff2be5998/2246494-3