Found another fairy that clears things up. You aren't supposed to not kill them after all it seems.
Viewing post in Funeral Song for the Elemental Lords comments
I made it to the True Lord of Love with only Wind powers. That was intense! I'm honestly not sure if I'm doing this the way you are supposed to or not but it was extraordinarily difficult compared to the rest of the game, though still very fun and rewarding. Looking forward to seeing where this all leads.