Hibari Otaka, a young woman who works part-time at a bar, has an all-consuming passion for wild hot springs, known in Japanese as noyu. These are natural, untouched geothermal pools found in remote locations, completely unconnected to any commercial bathhouse or human development. Her hobby is to travel alone across Japan to find and bathe in these hidden waters, a pursuit she dedicates all her free time to achieving.

Driven by an almost spiritual need, Hibari is fearless in her quest. She climbs mountains, treks through dense forests, crosses seas, scales ice walls, and explores mysterious caves, all for the reward of a solitary soak in a pristine natural bath. This deep-seated passion is a form of personal rebirth. In her past, Hibari was forced to give up her greatest love due to a traumatic accident, and her dedication to noyu became a way to rediscover a sense of purpose and reclaim her own identity, making every adventure a journey of healing. The story follows her as she visits various incredible locations across Japan, from volcanic islands and underwater springs to icy, snow-covered landscapes and hidden river caves.

The manga's episodic narrative chronicles Hibari's expeditions, detailing her preparations, the challenging journeys, and the euphoric, often sensual, release of finally immersing herself in a secluded hot spring. She is occasionally joined by her colleague from the Tasmania bar, Hichika, a chemistry graduate student who becomes fascinated by Hibari's passion and the science behind the springs, and accompanies her on some of the less extreme adventures. The central narrative arc of the third and final volume sees Hibari and Hichika set an ambitious new goal: to discover a completely new, previously unknown wild hot spring, which they call Hibari's Spring. Their search, which involves exploring many dead ends, culminates in a life-changing discovery that solidifies Hibari's bond with the natural world. The manga concludes as Hibari finds a profound sense of belonging, feeling that the sky, the mountains, and the hot spring water are all one with her.