The Valiante Kingdom has been conducting witch hunts for 17 years, but the targets are actually the Makai Knights and Alchemists, who protect humanity from Horrors - demons that possess souls consumed by sadness and pain. Makai Knight Leon Luis, 17, inherits the legendary Garo armor from his mother, who was killed by the kingdom, and struggles with the hatred he feels. His father, German, also a Makai Knight, trains Leon but decides to bring him along on a mission to the capital to investigate a surge in Horrors. Meanwhile, Prince Alfonso San Valiante is banished from the kingdom after being double-crossed, and he seeks help to reclaim the throne, intersecting with Leon's journey.