Fourteen Days on Koz Sar: Japanese Trio Opens New Line on the South Face

Japanese alpinists Takaaki Nagato, Ryo Masumoto and Hiroki Yamamoto have opened a major new route on the south face of Koz Sar (6,677 m) in Pakistan’s remote Batura Muztagh, with details of the August ascent now emerging through Yamamoto’s social media and international climbing media. 
The trio began climbing on 16 August 2026 and spent 14 days on the mountain in capsule style, progressively moving their equipment and camps up the wall rather than returning to Base Camp. They established six portaledge camps before all three reached the summit on 29 August, returning to Base Camp on 31 August. 

Their new route, “Waterfall Training,” follows an independent line up the south face for approximately 1,400 metres, comprising 39 pitches of rock and ice, followed by roughly 400 m along the snowy upper ridge to the summit. Reported difficulties reach 5.11a, A3, M6 and AI5. The name reflects the conditions encountered low on the face, where melting snow sent water continuously down the rock. The climbers also dealt with poor ice, rockfall and falls during the ascent.

Climbing History

Koz Sar has an interesting connection with Japanese mountaineering. An Anglo-Irish team made the first recorded attempt in 1993, climbing the south ridge and fixing ropes to around 5,800 m, before deteriorating snow conditions forced a retreat. 
The first ascent came on 17 August 1999, when an eight-member expedition from Japan’s Sendai Ichiko Alpine Club, led by Ichiro Yamagata, climbed through the south face onto the southwest ridge. Takashi Ota and Katsuyuki Kuriyagawa reached the 6,677 m summit after an expedition-style effort involving camps and extensive fixed ropes.
27 years later, Nagato, Masumoto and Yamamoto returned to Koz Sar with a very different approach, establishing a technically demanding, independent line up the south face over 14 continuous days.

Expedition Highlights

Peak: Koz Sar (6,677 m)
Range: Batura Muztagh, Karakoram, Pakistan
Climbers: Takaaki Nagato, Ryo Masumoto & Hiroki Yamamoto
Route: Waterfall Training,  new line on the South Face
Route Length: ~1,400 m + ~400 m summit ridge
Technical Difficulty: 5.11a / A3 / M6 / AI5
Pitches: 39
Style: Capsule style with six portaledge camps
Time on Mountain: 14 days
Summit: 29 August 2026
Achievement: Major independent new route on the South Face of Koz Sar

Photo courtesy: Hiroki Yamamoto's social media posts