Cerberus

The anime is set in a continent ruled by sword and magic called Kunaaan, where a power balance between the Holy Kingdom of Amoria, the Kingdom of Ishilfen, and the Vanrodis Kingdom keeps a peace so unstable that any tragedy that befalls any one kingdom will mean war for the entire continent. Another power, the evil dragon Daganzord, also resides on the continent, and no one is powerful enough to stop him from spreading destruction and charred land in his wake. Two individuals, Bairo and Kismitete, undertook a ritual alongside a party of wizards to seal Daganzord, but were foiled. This event was known thereafter as the Balbagoa Tragedy. Bairo and Kismitete's son Hiiro is saved by Giiru, and Hiiro swears to avenge his parents' deaths and trains himself with the sword. When Hiiro turns 16, he sets out on a journey to slay the dragon, and Giruu accompanies him, having no choice. Along the way, they meet many types of people, and gain companions on their journey. (Source: Anime News Network)