Mount Kobushi, Mountain peak in Chichibu-Tama-Kai National Park, Japan

Mount Kobushi reaches 2,475 meters in elevation and straddles three historical regions: Kai, Musashi, and Shinano. Several hiking routes lead to the summit, each offering different terrain and difficulty levels.

Mount Kobushi's name is commonly explained by its position at the meeting point of three historical provinces: Kōshū (Kai, now Yamanashi), Bushū (Musashi, now Saitama) and Shinshū (Shinano, now Nagano). A second explanation holds that the peak's shape resembles a clenched fist, since kobushi can mean fist. The mountain is listed among Japan's 100 Famous Mountains.

The name is commonly explained by the three old provinces meeting here: Kōshū (Kai), Bushū (Musashi) and Shinshū (Shinano); another explanation says the summit profile resembles a fist. The mountain is one of the 100 Famous Japanese Mountains, and from the top 43 of the other listed peaks can be seen.

The shortest route starts from the free car park at Mokidaira in Kawakami, Nagano, reached by bus from Shinano-Kawakami Station on the JR Koumi Line; the last stretch to Mokidaira is a walk of about 1 hour 15 minutes. From there the Chikuma River headwaters path leads to the summit and allows a day return if started early. The Yamanashi approach from the Nishizawa Valley entrance, via the Toku-chan New Trail, takes about 5 hours 40 minutes to climb.

The mountain serves as the source point for several major rivers including the Chikuma, Fuefuki, and Arakawa, which supply water to large regions. These waterways originate from the peak and feed into Japan's major river systems.