Nostalgic beauty rules this latest from the gentle animation juggernaut Studio Ghibli, in which Japan’s children of World War II come of age and come to terms with their country’s past. The plot is a sweet and simple high school love story; the setting is a nation readying for the 1964 Olympics and eager for acclimation in the modern world. With her mother studying abroad, self-starter Umi (voiced in English by Sarah Bolger) helps run her family’s seaside boarding house, daily raising a pair of semaphore flags in memory of her father, a ship captain lost in the Korean War. Sparks delicately fly when brash classmate Shun (voiced by Anton Yelchin) writes a poem about Umi’s flags for the school paper, which he publishes from a charmingly dilapidated clubhouse dedicated to extracurriculars — including a fierce student debate about whether to preserve the building or demolish it. As live-action, director Goro Miyazaki’s tale (from a graphic novel by Chizuru Takahashi and Tetsuro Sayama) would seem too slight, its past-becomes-future theme too obvious. Given the Ghibli touch, however, it’s gloriously light — long on reflective sincerity and tastefully moderated melodrama, short on all the panicked solicitation of kids’ attentions common to American animated films. Among the lovingly detailed, light-dappled landscapes and finishing postproduction touches via Skywalker Sound, other voices come through clearly, too, including those of Gillian Anderson, Beau Bridges, Christina Hendricks, and Chris Noth.