Boy goes to magic school. He can't use magic. Due to the circumstances which got him into the school in the first place, everybody thinks he's actually a top level magic user on par with the teachers. If anybody finds out that he really isn't, he gets expelled and the teacher he beat up gets fired. Said teacher is also the father of his romantic interest. Boy must survive on his wits and his physical strength. This is the spoiler free version, there's more to it than that.
Um... his older sister is a loli. Do you need anything more?
Okay. The tsundere girl is after his cock. Pic related.