18×2 Beyond Youthful Days is a 2024 romance film directed by Michihito Fujii and produced by Chang Chen. 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.

Adapted from a web travelogue by Taiwanese video game developer Jimmy Lai in 2014, the film was stuck in development hell before Japanese filmmaker Michihito Fujii joined the project in 2019, turning it into a collaborative film between Taiwan and Japan. Fujii spent four years penning the screenplay, while lead actors Hsu and Kiyohara were announced to be part of the production in March 2023. Principal photography commenced in Japan in the same month and continued in Taiwan in April. Following the completion of filming in May 2023, the film underwent six months of post-production.

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. It performed well at the box office and received generally positive reviews from critics, particularly for the acting and aesthetics, but the writing faced criticism. The film also secured four nominations in the 61st Golden Horse Awards.