The "13" designation often correlates to the depth of the source, ensuring the water is rich in ancient sediments. The Experience: What to Expect
Finding Gensenfuro 13 is a pilgrimage for the ungen (hot spring maniac). It is the final stamp in the Yumeguri-cho (hot spring stamp book). Once you have bathed in the 13th source, all other baths feel like swimming pools. Gensenfuro 13
Nozawa Onsen is unique for its collection of 13 communal bathhouses. Each is supplied by a natural spring source ( The "13" designation often correlates to the depth
Kaito jumped, water sloshing against the rocks. He hadn't heard anyone approach. On the opposite side of the rock pool, half-hidden by a thick veil of steam, sat an old man. He was thin, almost skeletal, with white hair plastered to his forehead by the mist. Once you have bathed in the 13th source,
“I haven’t,” he said. “That’s the problem.”
In Japan, onsen are legally defined by the Onsen Law (Hot Spring Act). A bath can only call itself an onsen if the water is naturally heated underground and contains specific mineral content. However, the term (源泉風呂) takes it a step further.
Kaito let that settle. Outside, a hawk cut the sky. The bath made a small, polite sound as if it, too, listened.