Medical melodramas generally either give you the diagnosis, fatal or otherwise, up front or save it for later in the story. In the former category is Michihito Fujii’s 2020 drama, “The Last Ten Years,” which signals the young protagonist’s fate — she only has a decade left to live — right in the title. In the latter is the director’s new tearjerker, “18×2 Beyond Youthful Days.”

Based on a travel essay by Jimmy Lai and scripted by Fujii, this Japan-Taiwan co-production delays its big reveal until nearly 90 minutes in. The intent may have been to heighten the poignancy, but for most of the film, I thought I was watching the story of a barely reciprocated teenage crush.

Hsu Kuang-han, who also goes by Greg Han and headlined the 2023 Taiwanese hit “Marry My Dead Body,” stars as the protagonist at ages 18 and 36. Kaya Kiyohara, who was brilliant as a romance-savvy teenager in the 2021 Koji Maeda comedy “You’re Not Normal Either!” plays his older love interest who consigns him to the “friend zone” from day one.