The second season was originally set for a 2021 debut with nothing more specific than that.
The manga comes from Eichi Shimizu an Tomohiro Shimoguchi which began in 2011 and has eleven volumes out so far.
Check out the official site and Twitter as well as the Netflix site.
With the pandemic having slowed down things in general, the official site announced through an event this week that the new season is set for a spring 2022 debut on Netflix.