Despite Kyouko Honda's tragic death, her vivid memory lives on, providing guidance through times of hardship to her close ones. However, Kyouko was not always the wise and radiant person that she is fondly remembered as in the present day. Feeling deserted by her own family and rejected by society, a young Kyouko abandons stability for a life of delinquency, jeopardizing her education and future. Fortunately, her descent into despair is interrupted by a fateful encounter with her husband-to-be Katsuya, who has recently started his teaching internship at her school. With a composure surprisingly unaffected by Kyouko's tantrums, Katsuya quickly wins her over through his gentleness and attention toward her—sincere gestures that she has never received before. As the two grow closer together, Kyouko opens her tormented heart to him and, along with it, a door to new horizons. [Written by MAL Rewrite]

Fruits Basket: Prelude centers on the Kyouko to Katsuya no Monogatari prequel, which covers part of the manga's 16th volume not shown in the television series. The movie also features a short compilation of the three-season anime and new scenes written by the author set after the original story. Mubichike cards with illustrations by Natsuki Takaya were made available on December 17, 2021. A Blu-ray version was commercialized exclusively at theaters screening the film, and limited edition items were distributed to the audience on a first-come, first-served basis. The gifts consisted of an original 16-page manga that established the setting for the new scenes as well as excerpts from the movie. Another Blu-ray was released on June 24, 2022, including a bonus eight-page manga booklet. Only in the first two days after its premiere, Fruits Basket: Prelude grossed a total of 33 million yen. Moreover, supplementary theaters held additional screenings to accommodate the greater turnout of viewers.