I was somewhat confused if “a Tengu is the incarnation of an angel in a wolf’s body” and not a race that Momiji can be born as a Tengu because biologically she would be just a wolf. Well we don’t know if / how angels reproduce so perhaps that’s why it took many years for her to be born.

I don’t remember the fate of Kaede but perhaps there’s a way to prolong her life? Tempest has extra magicules to spend (the dungeon is full of Veldora’s) but we don’t know if magicules capacity can be expanded easily (it happens e.g. in naming or evolution).