A member of the Amo-gumi and the senior (aniki) to the protagonist, Kanata Kotoge. Known as Kobayashi-no-aniki, "Army Knife Kobayashi," and "The Half-Devil, Half-Child." One of the most popular characters in the Amo-gumi, he is often cited alongside Hajime Noda and Soichiro Wanaka as part of the "Amo-gumi Big Three." He is a large man characterized by purple hair and a muscular build, standing at 186cm—the tallest in the group. While handsome, he constantly wears a wide-eyed, crazed smile that exudes an overwhelming sense of intimidation. Though relatively young in terms of age and tenure within the group, he is senior to Kotoge, Shion Kazuki, and Ryuki Aoyama. First person: I (casual/rough). In his childhood, he used "I" (soft/polite). While the Amo-gumi is full of eccentric "madmen" like Noda and Sunaga, Kobayashi is considered top-tier in his insanity, feared by his juniors alongside Koichi Nagase. Even Kotoge, who has hardened his spirit in the Amo-gumi, still trembles at Kobayashi's bloodlust. He also frequently subjects his juniors (especially Taiki Hayami) to unreasonable harassment. Despite his overwhelming combat ability, his personality is like that of a mischievous elementary school boy, and this gap makes him even more terrifying. However, he is fundamentally a man who cares for his comrades. He uses his combat skills to save juniors in a pinch and occasionally treats them to yakiniku. He is surprisingly prone to tears when a senior or junior passes away. When he went to assassinate the head of the Kyogoku-gumi, he acted alone without telling anyone his destination—a choice born from his strong desire that "no one else should die."

A junior member of the Amo-gumi. After Akutsu, the man who took him into the group, died in the line of duty, Iitoyo shaved his head into a very short buzz cut as a sign of resolve while seeking revenge. After the Mao War ended and he returned from his injuries, he stopped wearing his trademark pompadour and switched from a souvenir jacket to a tan suit, adopting a more traditional yakuza appearance. He refers to Kobayashi as "Kobayashi-no-aniki."

A combat-focused member of the Kyogoku-gumi. His birthday is Valentine's Day. His favorite sushi topping is yellowtail (though he gets the names of the fish he eats wrong every time). His main duties are leading raids and handling consultations for civilians. As one of the strongest in the Kyogoku-gumi, he can handle everything from instantly killing fodder to defeating the top-tier powerhouses of rival organizations. A young man with blonde hair in an undercut with lime green highlights. He has large, pitch-black eyes that lack highlights, giving him a yandere-like appearance. He stands 181cm tall, slightly taller than his junior, Kuga. He wears a blue dress shirt with sleeves rolled up to the elbows, white chinos, and black leather shoes. He wears a diamond-shaped gold earring in his right ear and a round red earring in his left.

"From today on, you're going to be people who 'used to exist'." A top-tier combatant of the "Mad Cartel." His alias is "The Crybaby of the Double Knives."