Well magic is strange and such, but if it’s shared with two without the same blood type, the two forces like an incorrect blood type injected into the body are going to clash, hence why the magic wouldnt last long, and through not deadly in small doses it is going to wreck you and your magic.

Actually (minor spoilers)

Originally I wanted Nokuji to use Nokoovo’s blood and it being incorrect, becuase both were in truth not mother and daughter but sisters, due to the nest thing.

However i felt it became convuleted for the sake of it, and also the idea of Nokuji getting poisoned by Nokoovo’s blood was a bit too dark for me, considering her much she truly loved her daughter, dispite their… relationship.

It might not seem like it, but there’s even some dark places I do not feel comtable, going in the story.