A young ronin who assumes the post of sword-tester. Asaemon's reputation is fearsome among the populace because he killed both his father and his first love. He performed the former at his father's insistence, as the terminally-ill man wanted to test his successor's swordsmanship in an act of seppuku; the latter was his first execution: a criminal who had seduced him as a boy years earlier.
He is atypical of portrayals of ronin in that he has a governmental post, owns a substantial house, and does not normally roam the countryside.
Years later, Asaemon is ordered by his superiors to kill Ogami Itto, but secret interference by Yagyu Retsudo causes his sword to become damaged. During his duel with Ogami, Asaemon's sword breaks, resulting in his death.