Minakami Onsen in Gunma Prefecture, is the source for the Tone River, Japan's biggest river. During the Spring melt, April - June, the river provides consistant grade 4 rapids for over 12kms of whitewater rafting bliss. There are a number of different courses available to cater for all levels, from nervous beginners to experienced rafting junkies. Canyons international team of professional guides will ensure you a safe and memorable day of rapid action.