Very, very shounen, to the point that part of me doubts it'll last very long. But I do like what this does differently. Fenrir isn't inherently malicious or evil like Sukuna, Uroro, or Kurama (at first). In fact she even starts out taking quite a liking to our MC for his animalistic ferocity in combat. Instead the conflict comes from the fact that she has a completely different set of beliefs from the MC, and is outright offended that he wants to use her power for something that goes directly against her beliefs. It's a culture clash rather than simple "good host vs evil prisoner", while still providing a solid foundation for a combative and antagonistic relationship between the two.
They also establish why the MC is so pivotal, since he's not just their strongest weapon against the vampires; he's literally the living lynchpin for the power system of this setting. It's a very real and tangible reason for the fight from here on to more or less revolve around the MC, because if he dies? Then the rest of humanity won't be far behind him.