However, his father went bankrupt due to business issues and Shiina was forced to work during the day and attempted to study at night.

Shiina graduating from Tokyo Imperial University in March 1923, entered the Ministry of Agriculture and Commerce, where he was assigned to the Engineering Bureau.

In 1925 he was one of the government officials who were dispatched nationwide to instruct and supervise important export goods and to promote the formation of cartels.

During this time, he visited Manchuria and negotiated with the South Manchurian Railway to operate regularly scheduled shipping connecting Nagoya Port and Dalian.

He was sent to Europe in August 1932 to observe the measures and industrial policies of the European countries during the Great Depression and returned home in May 1933.

At the request of Nobusuke Kishi, Shiina was one of the first officials of the Japanese Ministry of Commerce and Industry to join the new Manchukuo administration.

The survey was also conducted in remote areas of the country where marauders were still a problem, and covering agriculture, forestry, underground resources, and hydroelectric power sources.

Kishi, together with Yoshisuke Aikawa, offered him an executive role in the Manchurian Industrial Development Company, but Shiina refused and returned to Japan in April 1940.

Kozo Hayashi, Minister of Commerce and Industry, strongly opposed the draft plan of the new economic system, which created a conflict with Kishi.

Although Kishi was appointed as the deputy secretary at the end of the same year, he came under investigation by the prosecutor's office, under the auspices of the Minister of Interior, Keichiro Hiranuma.

When the Ministry of Munitions (Japan) was founded in November 1943, Tojo concurrently served as Minister, with Kishi as undersecretary and Shiina as the Director General of Mobilization.

In 1951 Shiina ran for a seat in the lower house during the 1952 Japanese general election; however, he was unable to obtain assistance from Kishi who had suffered a big loss the previous year.

Within the second Ichiro Hatoyama cabinet, Shiina became the Vice Chairman of the Democratic Party of Japan's political affairs, and was a member of the Transportation Committee.

In February 1957, the Kishi became Prime Minister and Shiina is appointed as the party's accounting bureau chief, even though he had only won one election.

Shiina won reelection for a third time in the 1960 Japanese general election, and was appointed Minister of International Trade and Industry in the second Hayato Ikeda cabinet.

When Tanaka decided to normalize diplomatic relations between Japan and the People's Republic of China, Shiina was sent as a special envoy to visit Taiwan to explain the situation to President Chiang Kai-shek.

Following LDP losses in the 1974 Japanese House of Councillors election and acrimony between Vice Prime Minister Takeo Miki and Finance Minister Takeo Fukuda, Tanaka asked that Shiina head a committee to reform the party and also asked Tanaka to determine his successor through discussions without an open election.

Shiina continued to serve as Vice President of the LDP under Miki, but soon had falling out over differences in policy over political contributions and the idea of a single-member constituency system.