KING'S GAME

The story begins when an entire high school class of 32 people receive a message on their cellphones from a person known only as the "King." The messages contain orders that the students must obey, or they risk the punishment of death. With their lives on the line, the students soon find out that the orders are getting more and more extreme as time goes on. (Source: Anime News Network) — Description from AniList community (anilist.co).