Kono Sekai ga Game da to, Ore dake ga Shitte Iru (WN)

Popular for being filled with bugs, the virtual-reality game New Communicate Online (a.k.a. Nekomimi Neko Offline).
A die-hard fan of the game, Sagara Souma, is sent to the game world from the power of a mysterious device.
Though surprised by the sudden turn of events, Souma conveniently knows the laws of the world.
Mastering every bug, using the game’s logic against it, he is soon known as “Maverick Swordsman Souma.”