Sword Art Online Alternative Gun Gale Online, Vol. 2 (light novel): Second Squad Jam: Start — Reki Kawahara

Though the official announcement of the second Squad Jam has come out, Karen Kohiruimaki barely shows any interest at all, despite being the champion of the first ferocious battle royale. Or at least, that was true right up to the moment she receives a cryptic message from a creepy stalker who informs her that on the night of the next Squad Jam, someone will die.
Now, LLENN needs to take up arms and cut through her inexplicable anguish to prevent her worst fears from coming true!