it doesn’t have to do with Sera specifically, it Has to do with the nymphs overall, And although her subplot eludes to what happens, you don’t really get details on her route
there was also the massacre, something else she wasn’t supposed to survive but that was because of an unforeseen sacrifice, not what you’ll find out soon
Oh, ok, I get it now. I got to that part in Katia’s route now. That was interesting.