You viewed them as emotionless tools, MC viewed them as his friends.
Not at all what I was talking about, but it's the second time someone said something, so I guess I'll try to be clearer in what I mean.
Ghoul+Skeleton(assume skeleton is same rank as ghoul)=Vampire makes sense to me. You're using two cards of similar strength/value to rank up and get a stronger card, with extra skills. Alternatively, a sort of ladder upgrade system with two of the same cards upgrading to the next tier makes it so even the lowest rank cards have value. So like, 16 crawling hands->8 skeletons->4 zombies->2ghouls->vampire. Instead, the game's system requires you to combine a lower ranked card with a higher ranked card to make the lower ranked card the same higher ranked card. If ghoul(c-rank)+vampire(b-rank) made a different species like a jiang-shi(b-rank) it'd make sense to me, but what's the point in making your ghoul a vampire instead of having a ghoul AND a vampire? Even if it's like Pokemon rules where you can only use X cards at a time, presumably there would be situations in which using the ghoul would be preferable to the vampire and vice versa, so there's still value in having both.
Obviously this is a manga so it's easier for the author/artist/story in general to not have a rotating cast of like, 20+ cards with fully fleshed out personalities. I'm just saying I think the system itself is badly designed from a gameplay perspective.