I was toying with the idea with Sakaki (of Azumanga Daioh) as being summoned as a familiar to Louise (Familiar of Zero). I didn't want to give Sakaki the powers of the Gandalfr that Saito had (superspeed, weapons mastery), and wanted something more reflective of Sakaki herself.
One option was to give her a better version of her natural talents -- Sakaki was physically adept, good at sports without even being competitive. She's also comparatively bright (which isn't really saying much, given some of the cast of Azumanga).
But how about affinity to animals? Either that, or animals and familiars treat her like kamineko does. Why brings me to the question: why _does_ kamineko bite her?
Among the theories I've seen is that kamineko simply dislikes sakaki. Not dislike as in the usual cat-dislike (if cats dislike you, they will (1) ignore you (2) leave your presence (3) hiss if you try to pet it/scratch if you persist (4) all of the above), but dislike as in "I enjoy giving you pain."
Story-wise, I was thinking of making ALL animals react this way to Sakaki. Upon being summoned, the students, as usual, taunt Louse... up until the bond they have with their familiars kick in and they realize that their familiars suddenly tense up in her presence, kinda like a herd of zebra that knows a lion is in the bushes; if you watch nature shows you'll see that the zebras don't run away unless the lion starts giving chase, and kamineko was unique in that he knew that Sakaki was actually harmless. The weaker familiars (frogs, cats, birds) avoid her, but the stronger ones would tend to act like Kamineko.
"That's right! A fire lizard! See, look at the tail. A flame this vivid and large means it's without a doubt a salamander from the Fire Dragon Mountains! It's like a brand! Collectors can't even put a price on these!"
"That's nice," Louise said, her voice bitter.
"Isn't it? It matches my affinity perfectly!"
"Your affinity is Fire, isn't it?"
"Of course. After all, I'm Kirche the Ardent. The ardent of gently -- Flame no! No eating other mages' familiars!" Sakaki had, apparently, tried to pet the salamander. Flame had his mouth wide open, teeth posed over Sakaki's bandaged hand. Kirche had had the salamander only for a day, but she had seen the same expression on its face when she fed it the night before with a side of beef she had smuggled from the kitchen.
Flame withdrew sullenly.
Or something to that effect.
Or, alternatively, Sakaki has animal affinity and befriends the various familiars with ease, Kamineko simply being a malicious exception. Hey, she had a pet wild cat. Not too fond of this -- less humor potential, and kinda makes Sakaki sue-ish.
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The rest of the cast were brought along with Sakaki being summoned, but not at the Tristain Academy. They end up in different parts of the continent, but I have to read more of the novels to form a idea where. Osaka turning out to be a void mage (and managing to found a new religion) is almost a given.