Jigoro Kuwajima

Jigoro is a small, aged man with pale skin, a lined forehead, and a many-pronged scar across his left cheekbone. His slicked white hair fluffs out around his head, and his right leg is missing, swapped for a wooden peg the anime stresses more than the manga. He wears a brownish-yellow jinbei bearing a faint triangle pattern, similar in style to Sakonji Urokodaki's garment, and supports himself on a heavy cane.

Dedicated and stern, he threw himself into raising the next generation of swordsmen and never gave up on a student. Although Zenitsu wept endlessly and kept trying to run away, Jigoro remained patient, satisfied just to watch the boy perfect one form. He likened the act of refining a skill through tireless repetition to forging steel, and his fatherly affection left him crushed when Kaigaku eventually betrayed all he had taught.

After holding the post of Thunder Hashira and then losing his leg in combat at thirty-five, Jigoro stepped down and turned to teaching. He first took on a troubled youth named Kaigaku, then saved Zenitsu from crushing debt and made him a pupil as well. Kaigaku mastered every form but the first, whereas Zenitsu, struck by lightning during his trials, could only manage the first form and nothing else.

Jigoro chose to name both boys his successors so that each might offset the other's shortcomings, a decision that quietly stoked Kaigaku's bitterness. When Kaigaku went over to the demons, the heartbroken old teacher ended his life through seppuku, a death made all the more agonizing because no one was there to deliver a clean finishing cut.

His tutelage shaped Zenitsu deeply. Near death from the Son Spider Demon's poison, Zenitsu calmed his breathing the way his master had drilled into him, and the news of Jigoro's fate sharpened his resolve to face Kaigaku. After Zenitsu killed his rival, the two met again beyond death, and a tearful Jigoro told the young man that he was what he cherished most.

Zenitsu went on to wear the old man's haori in place of his ruined one and carried the cremated ashes with him when he moved into the Kamado home. Jigoro's title was the uncommon Rumble Hashira, taken from an archaic word for thunder rather than the modern character used for the breathing style itself.