Maybe this is an old enough manga already that the "joke" of the dude being victimised all the time by the girls was oh-so-great comedy back then. That being said, I can't understand the whole point of Claire insisting Kamito must become her spirit. He's a bloody human. In Zero no Tsukaima Saito was, at least, summoned by Louise following the normal procedure, so in a manner of speaking he was a summoned creature. Here, however, Kamito is just another student. It feels like the author was a fan of Zero no Tsukaima, but didn't have the wits to understand what was going on in it, and thus copied that one element recklessly, thinking it's mighty good humour.