This paper provides a comprehensive analysis of the Bank of Japan’s (BOJ) recent experience in implementing the yield curve control (YCC) in the Japanese Government Bond (JGB) market. The YCC policy started in September 2016 with targets on two interest rates with different maturities: overnight policy interest rates at -0.1% and the longer-term 10-year JGB yields at zero percent, with a fixed but adjustable fluctuation allowance range. The YCC policy was highly effective in stabilizing interest rates at low levels, from short to long term, at least up to early 2022. This paper addresses the question of what the BOJ did under the YCC policy through the lens of the yield curve dynamics in the JGB and overnight index swap (OIS) markets. Empirical evidence demonstrates two points. First, the BOJ had very limited policy space to extract monetary easing effects by manipulating the yield curve at the introduction of the YCC policy. Second, the BOJ took the seemingly aggressive but actually reactive actions of outright JGB purchases to counter market pressures on the YCC cap. These findings indicate that the BOJ introduced a sustainable monetary policy framework of the YCC policy with the intention of shifting its focus to maintaining an extremely low interest rate environment for as long as necessary.