the story is very clear. They have been explaining many thing by episode 2. I guess you missed all.
Ms Lin is monster which can take human form. The fl is belong to nanshan hunter who hunt the monsters. The ml does not belong to any clans. Ms Lin, kill his mother and take over his mom identity. The ml doe not know that ms lins is a monster . I hope this help
https://x.com/Pandapandy19/status/1990741452452700408?s=20
https://x.com/mitchuu88/status/1990636364581494842?s=20
https://x.com/mitchuu88/status/1990610507443941508?s=20