Major character(s), not necessarily the main character, assume the role of a dungeon master. Dungeon master is a character that owned a dungeon, and is different from a dungeon guardian whose role is more readily attuned to dungeon's administration tasks.
After announcing it will be discontinuing all service, the internet game ‘Yggdrasil’ shut down… That was the plan, but for some reason, the player character did not log out some time after the server was closed. NPCs start to become sentient. A normal youth who loves gaming in the real world seemed to have been transported into an alternate world along with his guild, becoming the strongest mage with the appearance of a skeleton, Momonga. He leads his guild ‘Ainz Ooal Gown’ towards an unprecedented legendary fantasy adventure!
[You have entered the dungeon at Gwachun Station’s 1st Exit.] When former high school student Kang Woojin finds himself returned back to Earth after being forcibly summoned to a foreign planet for 20 years, he soon finds that Earth is not the same, normal place as he once remembered it to be. With his former strength and age reset back to zero, watch Kang Woojin as he gets back on the path to becoming the Earth’s strongest Necromancer!