In a peaceful alternate reality where the nuclear war of 199X never happened, the world of Fist of the North Star is transformed from a violent wasteland into a functioning modern-day Japan. The legendary martial artist Kenshiro is no longer a savior of a post-apocalyptic world but a hungry and unemployed young man wandering the streets. After being fired from a previous job, he finds himself desperate for money, leading him to pretend to be a cat in a bid to be adopted. He is taken in by a high school girl named Lin, who has also adopted his older brothers, Raoh and Toki, who were pretending to be a dog and a rabbit respectively.

The three brothers are reunited under the roof of Lin's father, Ryuken, who is alive and well and owns a small convenience store called Ryuryuken. While the store already employs Bat, a university student, there is a single part-time position available. However, due to the store's limited finances, only one of the three Hokuto brothers can be hired for the job. This sets the stage for the central conflict, as Kenshiro, the ambitious Raoh, and the often-scheming Toki find themselves pitted against one another, competing not only for the affection of the beautiful Yuria but also for the coveted part-time position.

Their rivalry is further complicated by the presence of the South Star District, led by the manipulative Shin, who also has a crush on Yuria. To stand a chance against this greater competition, the brothers are occasionally forced to put aside their bickering and work together. The narrative unfolds through a series of misadventures as the chibi-sized warriors struggle to adapt to the mundane challenges of modern life, such as holding down jobs and understanding basic societal norms, where their legendary martial arts skills are largely useless. The series also features other iconic characters from the original in absurdly reimagined roles, including a frequently naked Shin, a Rei with a stocking on his head, and the Holy Emperor Souther working as an English teacher.