Onrain (Online – The Novel) オンライン
Original author: Amagaeru Midori
Volume 1: A horror online game that one should never ever participate in…
One day, a mysterious parcel arrived.
Inside, there was a new type of game model I have never seen before.
That was the start of my horror.
A demonic game that is linked online.
……With that, game activated.
Adapted to a manga - "Online: The Comic"
Synopsis from Baka-Updates Manga:
22-year-old Yashiro Mai was an average office worker until the day a video game console
arrived in her mailbox and she was forced into playing a game known as “Nightmare.”
If you refuse to participate, those dear to you will die; if you lose battles in-game, parts of
your body cease functioning as penalty.
The horror of Nightmare spreads through society in a flash. To combat it, Mai’s company
creates a Nightmare Strategy Team, and she's one of the members.