Looking for a series; here's what I remember of it: The art style was about halfway between standard anime style and "Panty & Stocking", with characters being shorter/simpler/blockier than the usual fare, but still distinctly "anime". Lots of darker, more jagged effects to give the series a sort of "gothic" feel too, like the EDs of Nisemonogatari. As for the story, the protagonist is a wimpy teacher, and the female lead is a girl he protected from bullying years before. The girl practiced some form of spiral-based martial arts overseas(?) for a while so she could protect him in return. Can't remember who the major antagonist(s) is(/were), but there were definitely flashy confrontations fairly early into the story, interspersed with bits of the female lead being a poor student and needing to do retests. Oshiete! NU-fo-chan!