The original cut of the film (filmed in 2017 and shelved until its release in September 2020) was longer and darker, showing more of a disturbing reality of love hotels and with more graphic and longer sex and nudity scenes. Before the film was released, it was cut down in order to tone it down and attract a wider audience. This is also why most of Alexandra Daddario's nude scenes were heavily edited. For example, originally the "sex montage" was longer and it showed Margaret having rough sex with more men, and it also included some topless scenes from her. Despite rumors, there never was any full frontal or lesbian scenes filmed with her. Reportedly, the original cut was about 45 minutes longer than final version. Neither a director's cut nor an unrated version has been released.
In real life, Alexandra Daddario (Margaret) and Kate Easton (Louise) are close friends who shared a house together. Daddario has a YouTube channel on which she shows VBlogs with Easton.
In 2006, Kate Bosworth acquired the film rights to "Lost Girls & Love Hotels" by Canadian novelist Catherine Hanrahan. The film, which was to be titled after the novel, was to star Bosworth as the lead character Margaret and be her first foray as a producer.
In October 2017, it was announced that Alexandra Daddario would star in a newly produced adaptation under the title "I Am Not a Bird," which would later revert to its original title. Catherine Hanrahan was hired to adapt her own novel and William Olsson was hired to direct. The rest of the cast, including Carice van Houten and Takehiro Hira, was announced in November 2017.
Principal photography took place from October to December 2017 in Tokyo and Kyoto, Japan.