long ago, i read a novel similar to Zero no Tsukaima except that the summoned guy was op, the humanity was on the verge of extinction and the girl that summoned him was a student of a school that teach girls to fight the world menace. also, if you don't find it, just a novel where a human is summoned as a familiar and remain at least partially human
i don't remember and that's why i'm so lost but i remember near chapter 3 or so, the first monster attack the academy
hmm i dont think there are any novels on nu other than Zero no Tsukaima with a summoned human familiar. I think the novel you want would be an original or fanfic
I dont know but the only novel I know which has a man summond as a familiar is 'Ore to Kanojo ga Geboku de Dorei de Shuujuu Keiyaku '.
Ore to Kanojo ga Geboku de Dorei de Shuujuu Keiyaku This novel is similar to what you are looking for.