Starring Greg Hsu and Kaya Kiyohara, alongside an ensemble cast including Joseph Chang, Shunsuke Michieda, Haru Kuroki, Hitomi Kuroki, and Yutaka Matsushige, the film follows a recently fired Taiwanese video game developer (Hsu) on a solo trip to Japan, reminiscing about a past romantic entanglement with a Japanese backpacker (Kiyohara) that never blossomed into a relationship.

Fujii spent four years penning the screenplay, while lead actors Hsu and Kiyohara were announced to be part of the production in March 2023.

The film held its world premiere at Ambassador Theatres Taipei, on 14 February 2024, followed by a theatrical release on 14 March and 3 May in Taiwan and Japan, respectively.

In the present, Jimmy arrives in Matsumoto and encounters Liu, a Taiwanese izakaya owner who suggests that he visits Ami's hometown, Tadami.

On his journey, he meets a young backpacker named Koji on the Iiyama Line, who recommends they stop at the snowing Nagaoka, where Jimmy is captivated by the scenery, reminiscent of a classic romance film Love Letter.

However, after meeting and falling in love with Jimmy in Taiwan, her desire to continue living is ignited, and she decides to seek alternative treatments in Japan.

He reveals that he was aware of Ami's passing after completing his first game, where he fulfilled his promise to achieve his dream and attempted to reach out to her, but to no avail.

Jimmy expresses his gratitude for Ami's presence in his youthful days at the end of the letter, and promises to go on a trip without a destination in her honor.

Also appearing in the film are Toyoharu Kitamura as Shimada, the Japanese boss of Karaoke Kobe;[4] Buffy Chen as Hsiao-ting,[3] Jane Liao as Shu-yi,[5] Lee Kuan-yi as Wei, the co-workers of Jimmy and Ami at Karaoke Kobe;[6] and Figaro Tseng as Aaron, the co-founder of Jimmy's video game development studio.

[3] 18×2 Beyond Youthful Days is adapted from and based on real-life events recorded in a travelogue titled Wandering Journey on Slow Train in Japan (Chinese: 日本慢車流浪記), written by Jimmy Lai under the pseudonym "Blue Fox".

Lai, a Taiwanese video game developer, embarked on a vacation journey across Japan using the Seishun 18 Ticket and wrote the travelogue, aiming to reminisce about his romantic past with a Japanese backpacker.

[7][8] After publishing the travelogue on the Taiwanese blog Backpackers and it went viral in 2014, Lai was approached by film production studios interested in purchasing the adaptation rights.

[9] Eventually, producer Roger Huang acquired the rights and began searching for film directors and screenwriters to join the project.

[11][12] However, Lai became dissatisfied with the numerous screenplay drafts, feeling that the filmmakers and production companies were excessively expanding the story length and introducing new elements that deviated from the essence of his travelogue.

[10][14] However, he made numerous amendments, such as changing the story's background from Chiayi to Tainan, the hometown of Fujii's Taiwanese grandfather, as he found an older city more fitting for the film's tone.

[10] Fujii also added backstories for Jimmy, detailing his venture into starting his own video game company, and explored the reasons why Ami traveled to Taiwan, which further enhanced their character arcs.

[14][17] The film's production was officially announced under the working title Youth (Chinese: 青春) in March 2023, with Far EasTone as a major sponsor and starring Greg Hsu, Kaya Kiyohara, Hitomi Kuroki, and Chang Chen in lead roles.

[25] Taiwanese cinematographer Chan Chih-teng was initially attached to the project but had to withdraw since his wife was scheduled to give birth in the filming period.

[27][29] Other filming locations included Shibuya Excel Hotel Tokyu and Sumida Park in Tokyo, Matsumoto Castle in Nagano, and Yuigahama in Kanagawa.

[41] Hsu mentioned that the scenes revolving around the Karaoke were grouped together and filmed intensively, describing those shoots as having "boss-fighting level of difficulty".

[10] As the film was set in two separate timelines, Fujii personally drew storyboards for continuity editing to connect the junctions between scene changes.

[47] Michihito Fujii is a long-time fan of the band who started listening to their songs in his teenage years and personally invited them to contribute to the film, which he considers a "milestone in his career".

[51] The Taiwanese version of the official trailer was edited by filmmaker John Hsu, who shared a similar background with the protagonist Jimmy, as they both aspired to become video game developers in their early lives.

[63][64] By the end of the first weekend, it had accumulated a total gross of NT$28 million, securing the top position in the weekly box office.

[68] The film also grossed over JPY$176 million in the first weekend after its release in Japan, rising to the seventh spot in the Japanese weekly box office.

[75] Alan Chu, writing for United Daily News, lauded the film for its nostalgic and romantic elements, blending both Taiwanese and Japanese aesthetics, and its breathtaking cinematography.

He also commended Greg Hsu for his versatile performance and Kaya Kiyohara for delivering an emotionally moving portrayal, while acknowledging the star-studded supporting cast that further enhanced the film's appeal.

[76] CommonWealth Magazine's Sumi Chen shared a similar opinion, praising director Michihito Fujii's meticulous attention to detail, the authentic performances of the actors, and the film's skillful exploration of love, nostalgia, and cultural differences, ultimately considering it a compelling cinematic experience.