It's strange, right? So many people go to the mountain with no intention of killing themselves but end up dying anyway; Fuyuhi and Haruka went with the express purpose of killing themselves, but survived, and were allowed to leave the mountain. Does anyone have any theories about why? (Apart from "game plot required it.")
I can think of two possible reasons. It might have been partly about unresolved feelings - Fuyuhi still wanted to confess, even if Haruka already knew how she felt, and maybe deep down they wanted to die together as more of a lovers' suicide, rather than as part of a group. Or maybe it's about Haruka and her affinity with the maidens; Chiaki was influenced by the Isame, so you'd think the whole group would have died in the same way, but Haruka had greater potential, and either hadn't reached the point where she could return to the water yet, or by Glancing the others as they died, upgraded herself to Box-Class Maiden and was therefore too valuable to be allowed to drown in a lake. That doesn't really explain Fuyuhi, though.
I'd love to hear if anyone else has any ideas!