His father, Seiroku Kajiyama, was a prefectural assemblyman who later won a seat in the House of Representatives and rose to the positions of LDP Secretary-General and several Cabinet posts.

Kajiyama graduated from Nihon University and joined the Power Reactor and Nuclear Fuel Development Corporation in 1979, where he worked until 1985.

After a stint as his father's secretary from 1985 to 1988, he started a non-ferrous metals trading company and served as its president.

This came in the wake of the Moritomo Gakuen scandal, in which the government was accused of destroying records to cover up a favorable land-sale contract.

[1] As METI minister, he announced initiatives to phase out coal power in Japan in favor of renewable energy.