In the 21st century, rapid advancements in cybernetic technology lead to the creation of advanced androids known as kangoroids, initially designed for use as medical assistants in hospitals. The Ayanokouji Group, a leader in this field, begins developing a new line of home-use models under the code name Steel Angel. The first prototype, designated Kurumi, is completed and assigned to a specific monitor: Nakahito Kagura, a junior high student and the nephew of the corporation’s president. Suffering from trauma after a past incident, Nakahito has confined himself to his room, becoming a recluse. His situation changes dramatically when a package containing the hyperactive and loyal kangoroid Kurumi arrives at his apartment.

The main characters are drawn into Nakahito’s increasingly chaotic life. Kurumi is cheerful, devoted, and incredibly strong, though her clumsy and ditzy nature often creates more problems than it solves. Soon, two more kangoroids are sent to the same apartment: Saki, who is quiet and ladylike, and Karinka, who is temperamental and devious. The series follows the comedic and often chaotic domestic life of the troubled Nakahito as he learns to accept the unwavering devotion of his mechanical companions. The story is further complicated by the regular appearances of a strange woman and an eccentric delivery boy from the company, whose antics add to the general disorder. Unlike the original anime, which is set in an alternate Taisho period Japan, this live-action adaptation places the story in a contemporary setting. Over the course of the narrative, the initial embarrassment and reluctance Nakahito feels slowly give way as the kangoroids become an inseparable part of his world, leading to various adventures and conflicts involving the corporation and other individuals interested in the Steel Angel technology. The narrative focuses on the bonds formed between the boy and the artificial beings, culminating in a found-family dynamic amidst the surrounding chaos.