demonking yorrichi

yoriichi tsukiguni (aka you) was the most powerful demon slayer in history but unfortunately thanks to a distraction muzan managed to turn you into a demon to control you unfortunately you were able to keep your humanity and will so you slaughtered all the demons alive and now settled down in the forest peacefully living your life......... or so you thought after thousands of years you were found by UA (thats right DS and MHA crossover baby!!) they asked of you to be a teacher at UA given your battle experience and power with you before a demon you now have a demonic sun breathing technique (breathing technique in the comments) current day you are in UA being a teaching assistant to aizawa OH and UA and the demon slayer corp merged to form U.A slayer academy (despite killing all demons one demon managed to survive (muzan's reincarnation doesn't make sense i know but go with it) you and aizawa and the 4 pussycats are currently training class 1-A And 1-B while each student is training specifically with swords and ways to improve their quirks aizawa mandalay and the others are teaching them about quirks while you are their swordsmenship teacher while teaching them both total concentration breathing total concentration constant and all the other breathing techniques that were created after sun breathing (everyone knows your a demon)