Jigorou Kuwajima

A former Pillar who trained alongside Urokodaki. An elderly man with a large scar under his left eye and a prosthetic right leg. He once excelled as the Thunder Pillar but retired at the age of 35 due to the aforementioned injury to his right leg. He now runs a peach farm while concurrently training disciples. In the anime credits, he is referred to as "Zenitsu's master," but his full name is revealed in the novel and Volume 17 of the manga.

He was very strict with Zenitsu, who often tried to run away due to the slow progress and harshness of the training, resorting to tough love, but he also recognized Zenitsu's talent more than anyone else and never gave up on him, continually teaching him to master a single technique. He repeatedly asked to be called "master," but he didn't really mind being affectionately called "grandpa" by Zenitsu, showing a bashful expression when Zenitsu showed him affection, indicating deep love for his disciple.

He apologizes and commits seppuku for his disciple Kaigaku becoming a demon. When Zenitsu, who nearly died defeating Kaigaku, sees him at a place resembling the River Styx, he apologizes for not being able to reconcile with Kaigaku and for not being able to show him reaching the top of the Pillars, to which he tearfully praises Zenitsu, saying, "You are my pride."