Sword Art Online - Novel 13

Over two years ago, Kirito, the hero of SAO Crisis, landed in a mysterious fantasy world: Underworld. Halfway to the top of the Central Cathedral to escape the world for good, he and his friend Eugeo have now been separated. But Kirito doesn't give up and sets about climbing up from the outside. He has no choice but to co-operate with the enemy and is constantly threatened with death. Eugeo is hit even harder: he has to face the commander of the Integration Knights, Bercouli Synthesis One!