Souma Sagara, a lone gamer (bocchi), loves this online game "The Catfolk Realm" although it is famous for too much bugs. One day, Souma's cousin who was angry for him forgetting a promise with her, accidentally activates an ancient magic item which was found in their family's shed. And the next moment, he found himself inside that game as a living player! Souma remembers all the bugs and tips to play the game, so he enjoys living in the game world. But then he realizes something...he is living in this world, so what will happen to him when it's GAME OVER...!?