Hiko Seijuro is the name of the remarkable swordsman who taught the ancient technique of Hiten Mitsurugi Ryu to the young boy Shinta, who later would be known as Himura Kenshin. He met his apprentice one dark night when Kenshin was travelling with a band slave traders, the company was attacked by a group of bandits. Shinta's friends were killed along with the traders. Had Hiko not shown up, Shinta would have been slain, as well. Hiko performed his fast swordsmanship upon the bandits and saved the boy's life. He later decided to take young Shinta as his pupil and teach him Hiten Mitsurugi, renaming the boy as Himura Kenshin. The pupil later become a remarkable swordsman himself within the Ishin Shishi under the name of Battousai the Manslayer.
When he years later returned to Kyoto in order from the Meiji government to kill his assassin successor Makoto Shishio, Kenshin once again met his master and reconciled with him as a good apprentice and sword master. As Kenshin's master, Hiko is far more skilled in Hiten Mitsurugi Ryu than the pupil. Hiko Seijuro's signature weapon within the Hiten Mitsurugi Ryu is a shirasaya nihonto: a traditional katana with a scabbard and hilt in wood.
Hiko himself appears to be a fairly tall, broad-shouldered man in his late twenties, when he is actually in his late 40s.