After overcoming the Great Kanto Earthquake and financial panic, the Pacific War broke out in 1941. In the same year, Uyeno Unyu Shokai moved its central operations to Itozaki Oil Terminal in Seto Inland Sea in order to transport petroleum for the Japanese armed forces. As Rising Sun was a British company, its business operation was suspended and its property was placed under the enemy property control. As the No.1 gasoline carrier in Japan, Uyeno Unyu Shokai transported aviation fuel to Iwakuni and Noda by the order of the Army Aviation Headquarters.

Yutaka, the first son of Kametaro, graduated from Yokohama Commercial College in 1937 and joined his father's company. Before learning his job, he was drafted by the army and moved from one war area to another as an officer of a ship anti-aircraft artillery regiment. He returned to Japan, and in 1943 was promoted to captain in Hiroshima. In this period, he married Misao and made their home in Hiroshima.

On August 6, 1945, the atom bomb was dropped on Hiroshima. Yutaka was five kilometers away from the central explosion. On his way to Itsukaichi from his home, he was covered with the downpour of death ash. Had he been one kilometer closer, his life would have been endangered. As a result, he suffered symptoms of atomic bomb sickness such as fever, but he recovered after one year.

Following the war, for one year until he received an order from the oil distribution control company, Yutaka went to Osaka and engaged in the transportation of fish. He worked hard for cash to support his family and company. Business took a giant leap in 1948 when Uyeno signed the sole agent agreement with Shell Oil Company, which was renamed from Rising Sun Company. In order to concentrate on the transportation for Shell, Uyeno Unyu Shokai backed out of the management of Tsurumi Yuso, of which Yutaka was a director. At the same time, Uyeno returned the barges they were managing for Standard Oil. During the war, Uyeno was assigned to operate Shell Oil and Standard Oil's ships and barges placed under the enemy property control, and they were well-maintained. In addition to that, the news that Kametaro brought necessities to Shell personnel held as prisoners of war, reached the top management of Shell. As a result, Uyeno Unyu Shokai was appointed sole agent for Shell Oil Company in 1949. Yutaka Uyeno still has a vivid memory of that joyful day on which he signed the agreement.

In 1950, Uyeno began the road transportation of petroleum products exclusively for Shell Oil Company. Since that time, Uyeno has grown to be the second largest tank truck operator in Japan.