Situated in a quiet archipelago, Tatsumiyajima stands as a seemingly ordinary island where youth anticipate a tranquil existence. However, beneath this facade lies a stark reality. Amidst the serenity, a crucial battle unfolds to safeguard humanity against a mysterious adversary. The focal point of this conflict is the colossal mechanical warrior Fafner, a formidable protector of mankind's ultimate hope, standing as the vanguard in a crucial struggle for survival.