Taro Sakamoto is the protagonist of the manga Sakamoto Days. Once a legendary hitman, he now lives a quiet life running a small neighborhood store with his family. While he usually looks like a chubby, middle-aged shopkeeper, he unleashes his prime-era combat skills and mastery of using everyday objects as weapons whenever his family or daily life are threatened. Background and Identity Sakamoto is introduced as a figure admired by all hitmen and feared by all villains. He quit the life after falling in love with Aoi, who worked at a convenience store, and eventually married her and had a daughter. Currently, he is known as the manager of Sakamoto Days, portrayed as a man striving to protect the peace of his family. He remains the central axis between the mundane and the extraordinary as he gets entangled with the Japan Association of Assassins (JAA), its elite special task force ORDER, and the mysterious figure X (Slur).

The Sakamoto family consists of the father Taro, the mother Aoi, and their daughter Hana. Since the core of the story revolves around Sakamoto facing threats from assassins to protect his peaceful life, Aoi and Hana serve as the primary motivation for his actions. In particular, Sakamoto's rule of "never killing anyone" is closely tied to his goal of maintaining a normal family life. Aoi is the mother of the family and works as a clerk at Sakamoto Days. Despite Taro's past as a legendary killer, she is the reason he transitioned to a life of running a private store in a quiet town.

Lu Shaotang is a Chinese martial artist in Sakamoto Days. She is the daughter of a Chinese Mafia boss but lost her parents and was pursued by the Triad for the key to a family safe before being rescued by Sakamoto and Shin. She eventually joins Sakamoto Days as a clerk in charge of meat buns to gain independence. She is often seen accompanying the rest of the Sakamoto Days crew.

Shin Asakura is the sub-protagonist of Sakamoto Days, a telepath who can read minds and the partner of former hitman Taro Sakamoto. Initially approaching Sakamoto to persuade him to return to the underworld, he instead becomes a colleague at Sakamoto Days, fighting alongside him to protect their daily life. He is characterized by his blonde hair with a center part and a relatively small build. Partnership with Sakamoto Shin's telepathy isn't just a combat aid; it functions to convey the intentions of the nearly silent Sakamoto to the readers and other characters. Even when Sakamoto is silent, Shin reacts by reading his thoughts or the situation, leading to both comedic and strategic moments. The charm of this relationship lies in Shin's transformation from an "outsider trying to persuade Sakamoto" to a "comrade sharing the same ideals." Inspired by Sakamoto's dedication to his family, their bond is closer to a shared conviction than a mere contract. Shin is officially defined as a "growing partner," evolving from a supporting role into a capable fighter in his own right.

Heisuke Mashimo is a character in Sakamoto Days, a sniper connected to Sakamoto Days whose clumsy personality contrasts with his exceptional marksmanship. He is often seen with his companion, a yellow bird named Piisuke, helping Sakamoto. While he carries an air of being somewhat airheaded, he is a formidable sniper in actual combat. Due to his constant lack of money, he is often seen begging for food at Sakamoto Days, making him a relatable and comedic character rather than a typical cold-blooded killer. Piisuke is a yellow bird that is always with him. Heisuke is also known for participating in survival games hosted by the shopping district to win prize money.

Hana Sakamoto is the daughter of Taro Sakamoto in Sakamoto Days. As the story follows a retired hitman protecting his home and daily life, Hana is a core character representing the family that serves as Sakamoto's primary motivation for continuing to fight.