Taro Sakamoto is the protagonist of the manga Sakamoto Days. Once a legendary hitman, he now lives a quiet life running a small grocery store with his family. While he usually looks like a chubby, middle-aged shopkeeper, he unleashes his prime combat skills and mastery of everyday objects whenever his family or daily peace is threatened. Identity and Background Sakamoto is introduced as a figure admired by all hitmen and feared by villains. He quit the assassination business after falling in love with Aoi, who worked at a convenience store. He eventually married her, had a daughter, and now runs a private shop in a peaceful town. Currently known as the manager of Sakamoto Days, he is depicted as a man striving to protect his family and their peaceful routine. At the same time, 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 force ORDER, and the mysterious figure X (Slur).

The Sakamoto family consists of the father Taro Sakamoto, the mother Aoi Sakamoto, and their daughter Hana Sakamoto. Since the core of the work is Sakamoto facing threats from assassins to protect his family and peaceful life, Aoi and Hana serve as the narrative devices that explain Sakamoto's principles. In particular, Sakamoto's rule of "not killing anyone" is closely linked to his everyday goal of protecting his family. Aoi is the mother of the Sakamoto family and is introduced as a clerk at Sakamoto Days. Although Taro Sakamoto was a legendary hitman, he transitioned to a life of running a private shop in a quiet town after marrying Aoi and starting a family.

Lu Shaotang is a Chinese martial artist in the manga Sakamoto Days. She is the daughter of a Chinese mafia boss but lost her parents and was pursued by the Tan Syndicate for the key to the family safe before being rescued by Sakamoto and Shin. She later joins Sakamoto Days as the clerk in charge of meat buns to become independent. Shaotang travels with the Sakamoto Days family.

Shin Asakura is the sub-protagonist of the manga Sakamoto Days. He is a telepath who can read minds and is the partner of the former hitman Taro Sakamoto. Initially approaching Sakamoto to persuade him back into the business, he eventually becomes a colleague at Sakamoto Days, fighting alongside him to protect their family and daily life. He is characterized by his blonde hair with a middle part and a relatively small build. Shin and Sakamoto's Partnership The Importance of Telepathic Communication Shin's ability is not 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 reads his thoughts or the situation and reacts, leading to scenes that are both comedic and strategic. The charm of this relationship lies in Shin's transformation from an "outsider who came to persuade" to a "colleague who shares the same will." Because he was inspired by seeing Sakamoto fight to protect his family and daily life, their bond is closer to a shared belief than a contractual relationship. Role as a Growing Partner Shin is defined as a "growing partner" in official introductions. While he initially plays a large role in reading situations and assisting Sakamoto,

Heisuke Mashimo is a character in Sakamoto Days, a sniper connected to Sakamoto Days whose klutzy personality contrasts with his exceptional marksmanship. In the live-action film, he is portrayed by Junki Totsuka. He is mentioned as a character who helps Sakamoto alongside his partner, a yellow bird named Piisuke. Although Heisuke gives off a somewhat airheaded vibe on the surface, he is depicted as a man with undeniable sniping skills in actual combat. There is also a setting where he begs for food at Sakamoto Days due to a lack of money, making his down-to-earth and comedic character traits stand out more than a powerful killer image. Piisuke is introduced as the yellow bird that always accompanies Heisuke. He is also linked to an episode where he participates in a survival game hosted by the shopping district, aiming for the 1 million yen prize money.

Hana Sakamoto is introduced as the daughter of Taro Sakamoto in Sakamoto Days. As the story follows the former hitman Sakamoto protecting his home and daily life after retirement, Hana is a character positioned at the core of the family axis, serving as the primary motivation for Sakamoto to continue fighting.