https://twitter.com/imas_official/status/1946538980692164957
https://twitter.com/imas_official/status/1946539128235127255
https://twitter.com/imas_official/status/1946539255616176356
https://twitter.com/imas_official/status/1946539370317783338

FUTAM@S update:
https://idolmaster-official.jp/20th_anniversary/manhole

Miku's manhole (from July 30th) is located at north exit plaza of Rinku-Tokoname Station, Tokoname City, Aichi Prefecture
Toru's manhole (from September 26th) is located at Nagaoka Fireworks Museum, Nagaoka City, Niigata Prefecture
Minori's manhole (from October 11th) is located at north exit crossing of Shimodate Station, Chikusei City, Ibaraki Prefecture
Rinami's manhole (date TBA) is located near the entrance of Sunroad Shinshigai Shopping Arcade, Kumamoto City, Kumamoto Prefecture