The past three weeks have been something of a roller coaster ride for Masaaki Shirakawa, the former career central banker who was appointed Bank of Japan governor Wednesday by both chambers of the Diet.

Just last month, the 58-year-old was appointed BOJ deputy governor. But with the top post left vacant for the first time in postwar history due to political wrangling, Shirakawa had to take the role of acting governor as well. The five-year term of the previous governor, Toshihiko Fukui, ended March 19 without a replacement having been chosen.

After the Democratic Party of Japan-led opposition shot down two previous candidates chosen by the government — Toshiro Muto and Koji Tanami — the path was cleared for Shirakawa to step in to lead the central bank of the world's No. 2 economy.