Agatsuma Zen'itsu

When Zenitsu was younger, he was in love with a girl who tricked him into collecting money to get rid of his debts. Because of her, Zenitsu got into trouble, but he was saved by the former Thunder Pillar Jigoro Kuwajima. In order to pay him back, Zenitsu had to undergo hellish training and become a demon slayer.

Zenitsu was under the tutelage of Shihan and trained alongside his senior student Kaigaku. During one of their training sessions, Zenitsu climbed a tree because he did not want to train anymore and was suddenly struck by lightning, causing his hair to turn blond.

Zenitsu is a coward. He believes that he doesn't have long to live due to the dangers of being a demon hunter, which is why he often pesters girls he meets, asking them to marry him. Zenitsu has low self-esteem, which prevents him from living up to other people's expectations or his own. This often causes him to lose faith in his abilities, and even when it is obvious, Zenitsu denies that he has achieved victory on his own. He believes that his calling is to live a humble life, not to kill demons. When he senses difficulty or danger, he runs away, hides, or simply cries.

But even though he is soft, Zenitsu respects his comrades and admires his late teacher Shihan. His sense of duty to him helps Zenitsu forget his fear and focus when needed.

Over time, Zenitsu becomes more courageous in battle, as seen in his battles against Kaigaku and Muzan.

Zenitsu is a young man with fair skin. He has golden-brown eyes that are mostly downcast and short yellow hair of varying lengths that turns orange towards the tips. Before becoming a fighter, his hair was black.

He wears a lighter brown version of the standard Demon Slayer uniform. On top of the uniform, he wears a yellow-orange haori with a pattern of white triangles. On his feet, he wears a pair of kyahan, which are tied with white bows. The pattern on them matches the pattern on his haori.