Seiya, a teenager with a strong character, is used to participating in fights to earn enough to survive on the streets, while looking for his sister who has been kidnapped. During a fight, he unwittingly taps into unsuspected mystical powers and finds himself propelled into a world where he will encounter knights in armor, drawing their power from an ancient magical training and Athena, a reincarnated goddess who needs his protection. If he wants to survive, he will have to face his destiny and sacrifice everything to take his rightful place among the Knights of the Zodiac.