A combat member of the Yokohama-based yakuza organization "Shinjo-gumi." He is known by the alias "The Man Who Never Fails." While he uses polite language (keigo) with Rintaro Ichiai, Akira Nagato, and Taisei Hirose, he speaks casually with Goro Momoda. This suggests he is the youngest among the Shinjo-gumi combat members and holds the same rank as Momoda. He is a small young man characterized by black, outward-flipping medium-length hair with blue highlights at the tips and drooping eyes. One eye is hidden by his bangs. He wears a black rider's jacket with leopard print on the sleeves and collar, a black high-neck shirt, striped pants, and white sneakers. He is an extremely negative person who brings down the mood of those around him. In contrast to the upbeat and flashy Rintaro Ichiai, he leaves a gloomy impression, frequently saying, "I'll probably fail anyway." On the other hand, he is quite cynical and often directs sharp-tongued remarks even at his seniors (though they don't seem to mind). Despite his gloomy and negative demeanor, his respect for his seniors is genuine. He sincerely admires Nagato and Hirose as cool figures; upon hearing of Nagato's death, he repeatedly expressed regret for not being able to repay his kindness. Due to his negative personality, he is cautious enough to anticipate every scenario from the normal to the worst-case, and possesses high tactical planning abilities. Consequently, he serves as the field commander leading subordinates even during Ichiai's sabotage operations. As a combat yakuza, his small stature makes him ill-suited for power struggles, but he compensates by specializing in surprise tactics utilizing his speed and agility. He is highly proficient in ancient martial arts. His basic strategy involves silently taking the enemy's back with kunai or a kodachi, quickly closing in, and striking vital points.

"My name is Sakutaro Iito. Former invincible biker gang leader, now the junior with the strongest fists in the Amo-gumi." A new yakuza who joined the "Amo-gumi" in 2022. He was 20 years old at the time of joining. He originally served as the leader of a biker gang in his hometown of Kuon-cho for three years. After retiring, he worked as a mercenary fighter in Kuryu-gai (the Amo-gumi's base). According to him, he had an undefeated record in his hometown and was called "The Peerless Iito." One day, while he was spending his time fighting as usual, he was scouted by Toshiro Akutsu, the head of the Amo-gumi, and joined the family as everyone's junior. During his biker gang days, his weapons were his own fists, and his skill was powerful enough to justify his self-proclaimed peerlessness. However, after entering the underworld and having a run-in with Kosuke Kobayashi, he began using knives and handguns following the example of seniors like Kotoge, though he still uses his fists when necessary. Since joining the Amo-gumi, he has also studied martial arts, reaching a level where he could throw Kosei Kudo, a second-degree black belt in Judo.