The Kii Peninsula is the largest peninsula on the island of Honshū in Japan. It is named after the ancient Kii Province. The peninsula has long been a sacred place in Buddhism, Shinto, and Shugendo, and many people would visit from all over Japan as part of the Kumano religious practices.

Japan Median Tectonic Line , also Median Tectonic Line (MTL), is Japan's longest fault system. The MTL begins near Ibaraki Prefecture, where it connects with the Itoigawa-Shizuoka Tectonic Line (ISTL) and the Fossa Magna. It runs parallel to Japan's volcanic arc, passing through central Honshū to near Nagoya, through Mikawa Bay, then through the Inland Sea from the Kii Channel and Naruto Strait to Shikoku along the Sadamisaki Peninsula and the Bungo Channel and Hōyo Strait to Kyūshū.