After announcing it will be discontinuing all services, the internet game ‘Yggdrasil’ shut down. That was the plan, the player character did not log out sometime after the server was closed. NPCs start to become sentient. Moreover, a normal youth who loves gaming in the real world seemed to have been transported into an alternate world. This game becomes the strongest mage with the appearance of a skeleton, Momonga. The scene of this novel is quite similar to the How Not to Summon a Demon Lord light novel by Yukiya Murasaki.