Hmm, could it be just like the earlier commenter on one of the previous chapter, the angel and demon were also reborn? With the demon having a tragic end and the angel praying to save her. In the end they both have to serve as gods and that's why the demon emphatized more with Wen Ping?
No, in Chinese (and most asian countries) calling sister or 'Jiejie' (in Chinese) doesn't necessarily meaning they are biologically related, it's used as honorifics or term of endearment to address someone older (even by months) than the speaker.
But since they're celestial, I guess anything...
Just finished cleaning chapter 13 😅, I wanted to catch up before new volume comes out but unfortunately I only get to touch my laptop on weekends, anyways I'll try to close the gap this week.
Volume 2 is out! The whole volume is 6.32 yuan, if you have the means and you know your way around...
author/artist just gave birth and will be coming back to work next week. As for me, the scanlator, will be working on this, this weekend to catch up, before author releases new chaps.