He led the second successful attempt in 1977 to reach the summit of K2 and several other Japanese expeditions. Yoshizawa became a member of the Japanese Alpine Club in 1925 and later also a member of the American Alpine Club.
Yoshizawa's contributions to mountaineering are highlighted by his leadership in the second successful ascent of K2 in 1977, along with his participation in various Japanese expeditions. His membership in both the Japanese Alpine Club and the American Alpine Club further emphasizes his dedication to the sport.