 During his time at the ministry, Yamamoto studied abroad for two years at Cornell University's Samuel Curtis Johnson Graduate School of Management, where he acquired his MBA in 1975.After his return to Japan, he was stationed as head of the Iwakuni Tax Office in Yamaguchi Prefecture.Yamamoto subsequently took various postings within the Ministry of Finance and a visiting researcher position at Harvard University's Center for International Affairs, until 1987 when he took the role of head secretary for then Minister of Finance and future Prime Minister, Kiichi Miyazawa.