Following the 2011 M9 Tohoku-Oki earthquake, the interplate seismicity drastically increased in the downdip extension; however, it disappeared within the rupture area. An Mw7.0 earthquake occurred in the downdip extension off Miyagi in March 2021, followed by an Mw6.7 earthquake in May 2021. To examine the initial evolution of the next M9 earthquake cycle, we examined the regional seismicity and source processes of the two M~7 earthquakes. We found that the March Mw7.0 earthquake was nucleated at a conditionally stable patch where repeating earthquakes emerged after the Tohoku-Oki earthquake. The earthquake initiation from a conditionally stable patch at the deep plate boundary is probably a transient feature in the postseismic period of the previous M9 earthquake. The stress enhancement caused by the Mw7.0 event facilitated the subsequent May Mw6.7 earthquake. These two M~7 earthquakes ruptured the western seismic patches of the 1978 Mw7.5 Miyagi-Oki earthquake, which is the most recent typical earthquake in an ~40-year interval of M~7.5 earthquake sequence, and loaded the eastern shallow seismic patches for the sequence. Interplate seismicity in the updip area disappeared after the 2011 Tohoku-Oki earthquake. Assuming that the spatial pattern of interplate earthquakes will be restored to a situation similar to that before the Tohoku-Oki earthquake, the seismically active area should gradually expand to the updip area. Continued monitoring of interplate seismicity is essential to examine how plate-locking evolves during the M9 earthquake cycle.