The FMC's name is song yeonwoo a character from circles. I can't remember if she had seggs with the MC from circles though since she was a side character and the MC in this manwha(love quest) is a new MC.
If I remember correctly the artist himself published 2 doujin series both shotas
1. About apocalypse with a blonde and her shota
2. It's about femdom 2 femdoms and one shota. I was able to find the other one completed long time ago(the first one I mentioned) idk about this 2 femdoms and one...