In order to disguise himself, he wears badass glasses.

In the Edo period, there was a swordsman who held an incredible record that he was not once defeated in over a thousand contests between different schools of swordsmanship. According to a Japanese monastery clerk, there was a phantom of sword fighting that mastered things to the ultimate, recording until nothing has been left behind, and then disappearing, and Jin was the best student at the dojo that had been opened by that swordsman, he was called the young genius that surpassed the practitioners.

But, there was a certain incident that gave him enough reason to leave the dojo. Ever since, he has become a rounin. He has forsaken the swordsmanship where you cross swords with your opponent, and kills with a single stroke of the sword instead.