Logic doesn't apply normally to a story like this steeped in metaphor (which it was
not subtle about).
This isn't just a wacky story about a guy getting a half dozen copies of his girlfriend with different personalities, it's a challenge to him to test if he can walk the walk and actually love all of the girl he had a crush on but hadn't even seen in years. Including the parts he may have romanticized over time, and the parts that changed while he wasn't there. To say even a single Karin is one he can't love is to deny the actual Karin.
People compare this to 100GF a lot but it honestly reminds me more of
Uwagaki