King’s “the animation

Synopsis:

Kanazawa Nobuaki has rebuilt his life in a new high school far from his old one. Even though past horrors prevent him from befriending his new classmates. However, he manages to open up somewhat, especially thanks to the relay race during the sports festival. But one day, all the students receive a message from the "king" on their phones. No one takes it seriously, except Nobuaki, who knows that a terrible deadly game has just begun. The peace was short-lived…

Sources: Wakanim

Trailer:

The series: