Rokka no Yuusha

Legend says, when the Evil God awakens from the deepest of darkness, the god of fate will summon Six Braves and grant them with the power to save the world. Adlet Mayer, self-proclaimed "Strongest Man in the World," has arrived at the continent of Piena in hopes of becoming a Brave. Although it doesn't go as smoothly as he had planned, Adlet is ultimately chosen as one of the six heroes shortly after being greeted by Nashetania Loei Piena Augustra, crown princess and fellow Brave.
This story follows the two as they embark upon their destined journey to fight the Demon God, intending to meet up with their fellow heroes. However, when they finally unite, seven heroes are present, and soon the others begin to suspect Adlet to be a fraud. Now on the run, Adlet must utilize his unique skill set and wit in a fight for his life to identify which member of the group is the true impostor before it's too late!