 If you liked
Ousama Game
|
 ...then you might like
Caste Heaven
|
Taking place in a high school (bc which horror manga is complete without dumbass teenagers in a school setting?) both manga feature a king, who is in charge of a game that basically decides the lives of the participants of the game (aka the students). Taking part is mandatory, because those who don't participate, suffer serious consequences.
If you're a fan of the genre and are willing to overlook poor characters, little to no plot development, lots of plot holes and questionable decisions made by the characters, then both manga will prove to be entertaining for you.