After an earlier career working for a television broadcasting company, he entered the field of politics, serving as secretary to his politician father Mikio Aoki from 1999.

[4] Aoki attended Taisha High School [ja] in Shimane and graduated from Waseda University with a bachelor's degree in education in 1985.

[4] At this time Kazuhiko's name was immediately raised as a replacement, and he later received the official nomination to contest the Shimane district at the July 2010 election.

[6] In September 2014 Aoki was appointed by Prime Minister Shinzo Abe as a parliamentary vice-minister for Land, Infrastructure, Transport and Tourism alongside Kenichiro Ueno and Takashi Ōtsuka.

[11] In the election Aoki received 62.7% of the vote to defeat Hirohiko Fukushima, a nominally independent candidate who was jointly endorsed by the main opposition parties.

After Ishiba was elected and subsequently appointed prime minister, he made Aoki a Deputy Chief Cabinet Secretary.