Taro Sakamoto, a former legendary hitman, runs a small neighborhood store called Sakamoto Shoten in the Ikuraisaka shopping arcade. Though he has retired to a quiet life with his wife Aoi and daughter Hana, the shopping street itself remains a dangerous place where trouble frequently arises. Alongside Shin Asakura, a young telepathic former hitman who works at the store, Sakamoto must keep the peace while protecting his family and avoiding any bloodshed, honoring his promise to Aoi never to kill again.

The spinoff shifts focus from the larger conspiracy-driven narrative of the main series to the everyday challenges of maintaining order in the shopping district. Sakamoto and Shin work to improve public safety, catch shoplifters, and defend local businesses from gangs and disruptive elements. When they apprehend a shoplifter who later returns with his gang for revenge, they must subdue the threat without letting Hana notice anything amiss or leaving a mess behind. The pair also investigate the back alleys of the arcade, where they discover that Kashima, a figure from the original series, has been organizing business obstruction against legitimate storefronts. To counter the underground forces threatening the area, Sakamoto and Shin take on a new mission to recruit powerful allies. Members of the elite task force ORDER, including Sakamoto's former peer Yoichi Nagumo, also become involved as the situation escalates, and the story reveals new sides to these characters through their daily interactions and unexpected collaborations.

The central characters remain Taro Sakamoto, whose immense combat ability and no-kill discipline define every encounter, and Shin Asakura, whose mind-reading power and deep loyalty make him Sakamoto's indispensable partner and the reader's window into the protagonist's otherwise inscrutable thoughts. Aoi and Hana provide the emotional anchor for Sakamoto's peaceful life, while other familiar faces from the original series appear as allies or complications. The setting is the Ikuraisaka shopping arcade itself, a lively but volatile collection of small businesses where ordinary community life coexists with constant threats from the criminal underworld.

The tone is a daily gag comedy that centers on slice-of-life episodes and town revitalization efforts, though it retains flashy action sequences and battle elements. Recurring narrative arcs involve dealing with local gangs, uncovering the power structure behind the back alley factions, and balancing Sakamoto's desire for a normal family life with the inevitable intrusions of his past. The story is a spinoff of the Sakamoto Days manga, originally created by Yuto Suzuki, written and illustrated by Tetsu Okawa, and serialized in Saikyo Jump.