Kaitouranma The Animation

Shinjuro may be a little young to be the master of a swordsmanship school, but fate didn't give him a choice. Now his position and martial arts skill land him in the middle of serious trouble when the rogue samurai Mikage faces off against the Tokugawa government, and Shinjuro and the small group of swordsmen who train at the school must now protect the town from harm. However, the group won't be challenged until the Tokugawa house calls in a favor, and the young swordsman is forced to duel Mikage himself.

(Source: AniDB)