Rokka no Yuusha

Legend says the Goddess of Fate chooses 6 Braves marked with a flower to fight the Demon God when it returns. Adlet Mayer proudly calls himself the strongest man in the world and is eventually chosen as one of those heroes. He travels with Princess Nashetania to the meeting point, expecting to join 5 companions.

Instead, 7 marked warriors appear. One must be an impostor sent by the enemy, and the sacred alliance immediately collapses into suspicion. When the evidence points toward Adlet, he is forced to flee while trying to prove his innocence and identify the real fake before the chosen heroes destroy one another without ever reaching the Demon God.