Fifteen years have passed since the events of Dragon Knight 3. Takeru and Luna have settled into a quiet life—until a mysterious force erupts from another time and tears open the peace they have built. When word arrives requesting his aid, Takeru makes an unexpected call: he sends his son Kakeru instead. His old comrade Baan responds in kind by dispatching his own son Sail alongside Kakeru. Together, the two sons carry the weight of their fathers' legacies into a conflict that neither of them chose—but both of them will have to see through.