Yamataro, a brown bear cub orphaned shortly after birth, is rescued from a drifting ice floe by humans. Confined in captivity, he is tethered near a bustling train station as a spectacle for passersby. There, he forges a profound connection with Shi-roku, a class C62 steam locomotive, who becomes his steadfast companion and unexpected mentor. The locomotive teaches him survival techniques, including mimicking its steam whistle. Inspired by their bond, Yamataro escapes human dominion, fleeing into the wilderness to reclaim his autonomy. Years later, as a mature bear, he shares a fateful reunion with Shi-roku, now weathered by time, poignantly reflecting the enduring legacy of their bond. His journey traces an arc from fragile orphan to self-reliant survivor, forged through his bond with the locomotive and the trials of reintegrating into the untamed world.