While looking over recent series with more than one season, I came across Hitori No Shita. And I was hooked! Watched it all in a few days.
The story goes, Soran's grand father had an incredible martial art style he passed onto his grand son. His grand father enlisted an immortal girl, Houhou, to guard Soran.
While Soran seeks the truth about his grand father's past, he's also seeking any clues to Houhou's past. 2nd season focuses on a martial arts tournament. Check it out !