Arc the Lad begins with the main character, Arc, a young man who grew up in a small village in the northern part of the world. He had a peaceful life but was forced to face an unexpected event when his village was attacked by monsters from another world. This attack was a sign of something far more dangerous that was about to unfold. During his journey, Arc encounters a group of companions, each with their own unique abilities and backstories, including Galdo, Lutz, and Choko, who are key characters in the story. Later, they discover that the events were the result of an attempt by a secret organization to harness the power of beings known as "otherworldly creatures," which have the potential to destroy the world.