Summer Nightmare

One day, a boy, Riel, has a nightmare. inside the dream there is a school just like in real where terrifying things continues to happen.
Being chased by a blood-soaked medusa, his friends are killed.
Students foam teams just to fight each other.
...this was a beginning of [Nightmare Game].
After inference of collected hints, they can end this game.
the [Broadcast] will tell about where Hints are, and friends' death.
they were programmed to bring them to death.
is the [Broadcast] from my mind? and what happened in dreams is connected to reality.
when someone dies in my dream- so do in reality. can Riel finish the game?