Sano attended the 23rd class Imperial Japanese Army Academy and graduated in 1911. In 1913, he attended the IJA's artillery and engineering school, graduating in 1914. Sano completed the 31st class of the Army Staff College in 1922. He was promoted to major in 1926, he was assigned as a military attaché to Great Britain from 1927 through 1928.
From 1931 through 1933, Sano was assigned to the 4th Artillery Regiment. For the next two years, he worked in the IJA 5th Division and briefly commanded the 25th Field Artillery Regiment. He was promoted to colonel in 1935. From 1935 to 1936 Sano was assigned to the IJA 12th Division, and then once again commanded the 25th Artillery until 1937. From 1937 until 1938, he was Chief of Staff of the IJA 14th Division, and then commanded the 4th Heavy Field Artillery Brigade. Sano was promoted to major general in 1938. For one year beginning in 1940, Sano commanded the IJA's Field Artillery School. In 1941, he was promoted to lieutenant general.
Hong Kong and Sumatra
In 1941, Sano assumed command of the 38th Division. Early in the Pacific War, Sano and his division participated in the Battle of Hong Kong by invading Hong Kong Island on December 18, 1941. The British garrison surrendered on December 25, 1941. Sano's troops were reported to have committed atrocities against civilians in Hong Kong and British prisoners of war (Major General Takeo Itō, Sano's subordinate and commander of the 38th's Infantry Group, was tried and convicted after the war for war crimes). The division then transferred to Sumatra and participated in the Netherlands East Indies campaign.
The 38th Division was then transferred to Rabaul, New Britain in the Southwest Pacific in September 1942 in order to participate in the Japanese attempts to retake Guadalcanal from Allied forces during the Guadalcanal campaign. Two battalions from Sano's division were delivered to Guadalcanal by Tokyo Express missions in October 1942 and participated in the Battle for Henderson Field, which resulted in a decisive defeat for the Japanese forces.
In November 1942, Tokyo Express missions delivered the 38th Division's 228th Infantry Regiment to Guadalcanal along with Sano and his staff. The Japanese attempted to deliver the remaining 7,000 troops of the 38th Division by slow transport but the effort was defeated during the Naval Battle of Guadalcanal from November 12 through November 15, 1942. Only about 3,000 of Sano's troops successfully reached the island and most of their supplies and heavy equipment were lost. After suffering losses during the Battle of Mount Austen, the Galloping Horse, and the Sea Horse, Sano and the remainder of his troops on Guadalcanal, about 2,316 men, were evacuated during Operation Ke on February 2, 1943, giving control of the island completely to Allied forces.
Japan, China, and death
After returning to Rabaul with his troops, Sano was reassigned to Japan and assigned as Chief of Staff of the General Defense Command (GDC) in 1943. The GDC administered all IJA line and training units in the Japanese home islands and Korea. He then served on the General Staff until 1944.
Sano was sent to China and given command of the IJA 34th Army in Hankow in July 1944. In May 1945, Sano and the 34th Army were transferred to Manchukuo and northern Korea under the control of the Kwantung Army. Sano became ill and died on July 3, 1945.