Magical Explorer, Vol. 5 (light novel)

Far from pleased that Kousuke has been appointed to the Ceremonial Committee, Gabby challenges him to a dungeon-clearing competition where it's win or step down from their positions. Despite the high stakes, Kousuke agrees to her terms knowing that he can exploit Gabby's bond with her brother Benito to guide everyone to the game's Good Ending. But will he really be able to drive out the darkness weighing on Gabby's heart?