This Is Another World [1] The Undead King

This Is Another World is a series of 'isekai' books who tell us the story of Shimon, a stories lover who was summoned into the Twilight Dungeon, the most dangerous dungeon in all this fantasy world, and that met Astaroth, the most powerful [Undead] in the world, who make a deal with this in order to obtain the knowledge storaged in his smart-phone.

This is the story of how a story lover becomes the disciple of the Undead King, in order to be free of the Twilight Dungeon and meet the fantastic world of Eltera.