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 top-tier combat skills and the ability to weaponize everyday objects whenever his family or daily peace are threatened. Identity & Background Sakamoto is introduced as a figure once 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 opened a private shop in a peaceful town. Currently known as the manager of Sakamoto Store, he is depicted as a man striving to protect his family and their peaceful life. He remains the central axis of the story as the boundaries between the mundane and the extraordinary blur, involving 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's peace, Aoi and Hana serve as the primary motivation for his actions. In particular, Sakamoto's "no-kill" policy 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 the Sakamoto Store. 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. The daughter of a Chinese mafia boss, she lost her parents and was pursued by the Tan Association for the key to her family's heirloom vault before being rescued by Sakamoto and Shin. She later joins the Sakamoto Store as the clerk in charge of meat buns to gain independence. Shaotang often accompanies the Sakamoto Store family on their adventures.

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 eventually becomes a colleague at the Sakamoto Store, fighting alongside him to protect their daily lives. He is characterized by his blonde hair with a center part and a relatively small build. Partnership with Sakamoto Importance of Telepathic Communication Shin's ability is not just a combat aid; it serves to convey the intentions of the nearly silent Sakamoto to the readers and other characters. Even when Sakamoto remains quiet, Shin reacts by reading his thoughts or the situation, leading to scenes where their chemistry is both comedic and strategic. The charm of this relationship lies in Shin's transformation from an "outsider trying to persuade" to a "comrade sharing the same will." Because he was moved by seeing Sakamoto fight for his family and peace, their bond is closer to a shared conviction than a mere contract. Role as a Growing Partner Shin is defined in official introductions as a "growing partner." While he starts by reading situations and assisting Sakamoto,

Heisuke Mashimo is a character in Sakamoto Days, a sniper connected to the Sakamoto Store whose airheaded personality contrasts with his exceptional marksmanship. In the live-action film, he is portrayed by Junki Totsuka. He is often seen helping Sakamoto alongside his companion, a yellow bird named Piisuke. While Heisuke gives off a somewhat scatterbrained vibe, he is depicted as a reliable sniper in actual combat. There is also a recurring gag where he begs for food at the Sakamoto Store due to being broke, making him a more relatable and comedic character rather than a typical cold-blooded killer. Piisuke is introduced as the yellow bird that always accompanies Heisuke. Heisuke is also involved in episodes such as participating in a survival game hosted by the shopping district to win a 1 million yen prize.

Hana Sakamoto is the daughter of Taro Sakamoto in Sakamoto Days. Since the story follows former hitman Sakamoto protecting his home and daily life after retirement, Hana is a central character representing the family that serves as his core motivation to keep fighting.