Mochizuki was elected to the first of his four terms in the city assembly of Shimizu in 1975 and to the first of his two terms in the assembly of Shizuoka Prefecture in 1991.
He was elected to the House of Representatives for the first time in 1996 as an independent. He was affiliated to the openly revisionist organization Nippon Kaigi.[1]
Mochizuki died in office at the age of 72 on 19 December 2019.[2]