"Shinobi Life" is a manga series that blends elements of romance, fantasy, and historical fiction. The narrative centers around Kagetora, a ninja from the Sengoku period, who is transported to the modern world through a time-traveling accident. In the present day, he encounters Beni Fujiwara, a high school girl and the daughter of a wealthy businessman. Kagetora mistakenly believes Beni to be the reincarnation of Princess Beni-hime, whom he was sworn to protect in his own time. Despite her initial skepticism, Beni becomes entangled in Kagetora's life as he adjusts to the modern world while grappling with his sense of duty and loyalty.

The story explores the evolving relationship between Kagetora and Beni, as well as the challenges they face together. Kagetora's ninja skills and traditional values often clash with the realities of contemporary life, creating both comedic and dramatic moments. As their bond deepens, the narrative delves into themes of identity, love, and the tension between past and present. The series also introduces other characters, including Kagetora's fellow ninja and adversaries from his time, who occasionally cross into the modern world, adding layers of conflict and intrigue.

The plot intertwines Kagetora's quest to fulfill his duty with Beni's personal struggles, including her strained relationship with her father and her own search for purpose. The manga balances action sequences with emotional depth, as Kagetora's unwavering loyalty and Beni's growing affection for him drive the story forward. The series concludes with a resolution that ties together the historical and modern elements, offering a satisfying conclusion to the characters' journeys.