Land of the Lustrous - Wikipedia

Houseki no Kuni Wiki

Yellow Diamond, Houseki no Kuni Wiki

The Decagon House Murders (manga) - Wikipedia

I can't tell if this is true but I sort of hope so that something like this is out there : r/LandoftheLustrous

I started to read Sakuhinshuu the other manga of ichikawa and found this. (Check the wiki for Kannon there are at least 10 differents evidences that makes it looks like it's Phos)

Final Impressions: Land of the Lustrous (Houseki no Kuni)

Urusei Yatsura (1981 TV series) - Wikipedia

Final Impressions: Land of the Lustrous (Houseki no Kuni)

Maaya Uchida - Wikipedia

Tokyo Ghoul (film) - Wikipedia