The Child of Calamity and the Saints' Labyrinth

A boy born from this world alongside the summoners from Japan... They will challenge the max-difficulty dungeon! God created a labyrinth, which people challenge with guns, swords, and magic in an RPG-like world. Summoners from many other worlds participate in this massive battle! The locally born hunter Shun quickly rises to prominence as he plays the game!! Then, he meets the twins Yua and Yuna, who have been summoned from Japan... *Note: Chapter count includes one extra chapter.*