On December 10–13, 2020, Shirai, a post-graduate at NSSU, competed again at the 2020 All-Japan Championships in Takasaki, Japan. He did not as well as in past years, ranking just 18th on individual AA (167.196), and 4th on FX (15.166). Japan's AG federation repurposed this event in being an extra Olympic-qualifying chance as event updated to the most in-form roster nearest to Games, which the COVID-affected 2020 Summer Olympics in Tokyo, Japan, got put off until next summer, in a 6-man team—4 men in team AA finals with team bronze at 2018's WC that Shirai posted 3 scores on FX, VT and HB to team total, and 2 more as event individuals.