According to the people of Hotto, Tatsunaga was recently battled by a young man named Ryu. Ryu successfully slew the dragon, but lost his life in the process. He was the son of Miko, the effective leader of the village. This story does not come into play until the second act of Dragon Quest XI, when the Hero and party investigate rumors of a monster at the nearby volcano and encounter the siblings Atsuo and Atsuko. The young brother and sister reveal that Miko plans to sacrifice their mother as part of a rite. Atsuo asks the party to help him investigate why Miko would order such a horrible thing, and they explore Mount Huji. They soon finds Tatsunaga asleep in the caverns. Atsuo draws the conclusion that Miko lied about Ryu slaying the dragon and now wants to feed her own people to it, and he and the party quietly escape before the dragon wakes up.
The party returns to Hotto, where Atsuo confronts Miko and exposes her deception in front of the villagers. However, before Miko is able to explain or to defend herself, Tatsunaga suddenly flies into Hotto. Miko runs down to the dragon, interposing herself between it and the shocked villagers, and says that the dragon is only "a boy." She turns to face Tatsunaga, which eats her in a single bite, terrifying the people of Hotto. The Hero and his companions rush to the dragon and fight it to protect the villagers. However, just as they are about to land the finishing blow, Tatsunaga flies off and retreats to its lair.
Then, the party and Atsuo find Miko's diary, which reveals the shocking truth about Tatsunaga. Ryu did indeed slay the dragon, but it breathed a strange smoke on him just before dying. A curse took hold, and Ryu transformed into the dragon he had only just defeated. Miko did all she could to break the curse, but could not find a method of doing so. Ryu/Tatsunaga then started to hunger for humans, and Miko ended up prioritizing her son over the people of Hotto, and planned a sacrifice to satiate the dragon's hunger. The Hero and company also learn that Miko had almost found a cure, but Tatsunaga had eaten it with her. They decide that, sadly, Ryu has lost all of his humanity by now and must be defeated.
The Hero and his party members enter Mount Huji once again and confront Tatsunaga in a second, more difficult battle. This time, they defeat him for good.