Onishi Bozu Jigoku is a grey mud hell in the Kannawa district, where thick mineral clay bubbles up in slow grey domes that inflate and burst with a satisfying plop. The bubbling grey mud creates a different visual experience from the more colourful water hells — this one is primordial and slightly comic, the surface resembling a pot of very thick porridge at boil.
The site is one of the quieter hells and worth including in a circuit for the contrast it provides. The facility is small and can be seen in 15 minutes. Foot baths heated by the spring are available on-site. Located within walking distance of Umi Jigoku in the main Kannawa cluster.