Kamui's less likely to be vocal on the topic, but he has a kind heart.

[ Doubtless, the existence of a certain hunter-turned-vampire would color what Kamui has to say on the matter, but Subaru knows him better than anyone. His twin may come across as much the same as an unfriendly cat, but that isn't who he is deep down.

So while Kamui might not admit his concerns, or may voice them in a way that belied what he actually felt, Subaru feels he can give his assessment with confidence.

...But yes, no one is quite as soft as Subaru, probably. ]

He only ever gave his blood in one instance, to save someone. And only then to honor an agreement.

[ And that was only because he wouldn't let Subaru pay that price again. CLAMPires. ]