Truck Uketome Isekai Tensei!: Nekketsu Butouha Koukousei Wataru!!

It's a wonderful day for Wataru Ito, high school student, master martial artist, honorable and humble teenager, and all-around awesome guy. During his daily run to school he happened to get hit by a large truck barreling around a corner. Not that this is the kind of event that would be the end of the likes of Wataru, of course, but when a truck runs into you, you get sent to another world. That's just the way things are sometimes. Still, Wataru's not about to take this kind of thing lying down! The first thing he sets out to do is find who's the toughest hombre in this land and go up against the greatest challenges this new world has to offer! Oh, and the greatest fighter in this place also happens to be the Demon Lord who is kidnapping people all across the kingdom in an attempt to wipe out humanity? Even better! Wataru's main interest is in facing a tough battle; saving the world in the process is just icing on the cake!

(Source: J-Novel Club)