University of Tokyo.
Hikokichi was appointed consul at Chefoo in China in 1893. He served again in China as consul general at Tientsin from 1901 to 1907. He was appointed ambassador to Pekin in 1908.
On 4 September 1909, he signed the Japan-China Agreement concerning Kando as the Japanese ambassador to the Ching Empire in Beijing.
During the Chinese revolution broke out in October 1911, together with then foreign minister Uchida Yasuya, he argued for the provision of support to the Ching government during the 1911 Chinese revolution. His term as ambassador to Pekin lasted until 1913.
Then, he was appointed the Japanese ambassador to Rome in 1916 and in office until 1920. Hikokichi is described as a conservative ambassador.
On the other hand, then prime minister Hara Takashi wanted Hikokichi to search for European institutions of public information when the latter was ambassador and a Versailles delegate.
Ijuin reported that the best way to create an influential information bureau was to coordinate all information sources, including army, navy and finance ministry. Eventually, a public information office (Gaimusho Johobu) in the ministry of foreign affairs was established on 13 August 1921, and Hikokichi was appointed its head Then he served as governor-general of Kwantung Leased Territory in northeastern China for one year.
He was appointed on 8 September 1922, replacing Isaburo Yamagata as the governor-general.
Hikokichi was in office until 19 September 1923. Then he was appointed foreign minister on 19 September 1923 to the second cabinet of Gombei Yamamoto, replacing him who also assumed the role of foreign minister briefly from 2 to 19 September.
Hikokichi was replaced by Keishiro Matsui on 7 January 1924 when a new cabinet was formed by Keigo Kiyoura. Shortly after his removal from the office, Hikokichi died of neuralgia in Tokyo in April 1924.
During his tenure, he was one of the leading members of Japanese delegation at the Paris Peace Conference in 1919.