OUSAMA GAME

Ousama Game summary:

A mysterious command arrives from a "King".
The life-threatening "Game" has now begun for the 32 students of the first year's B Class.
One day, all of the students in Nobuaki's class received their first message from someone calling themselves the "King", in which was written a baffling command.
That first command was very easy. However, the commands began to escalate until a life-threatening game had begun.
Failing to obey the orders leads to death!! Their friendships are being undermined by a bottomless terror!!

(https://www.animenewsnetwork.com/encyclopedia/anime.php?id=19973)
Official English translation on Comico's (https://www.comico.io/pocket-comics) (colored webcomic version)

A mysterious command arrives from a King. The life-threatening Game has now begun for the 32 students of the first year's B Class. One day, all of the students in Nobuaki's class received their first message from someone calling themselves the King