Inside the Volcano: Restricted Trek, pH 1.7 Onsen & Caldera Winery

Follow the path of volcanic energy from its source inside Mount Io down to a glass of local wine. Begin within the off-limits crater zone, passing boundary ropes with a certified guide to hike among 1,500 active fumaroles. Next, dig into the lakeside sand at Sunayu beach with your hands to feel the rising geothermal heat, before immersing yourself in Kawayu Onsen, one of the world's most acidic hot springs (pH 1.7). The day concludes with a private tasting at Kussharo Caldera Winery, where this mineral-rich volcanic soil yields a rare, cool-climate natural wine. You will leave with a firsthand understanding of how a single living volcano shapes the landscape, the water, and the flavors of this remote corner of Hokkaido.