A la conclusión del combate contra Hydra, Katalina le dice a Gran algo que cambiará su vida por completo. Ese hecho será el detonante para que Gran decida salir de su pueblo de una vez por todas.

Gran and his party depart Zinkenstill for their goal, the Island of Astrals. However, Katalina crash lands the small airship on a nearby island, Eingana Island. A man named Rackam happens to witness their totaled aircraft. The townspeople consider Rackam an oddball for the way he's always working on repairing a certain airship that has no chance of ever flying again.

Gran y compañía parecen haber encontrado un timonel apto, pero Rackam se niega a colaborar porque en el caso de volar, tiene que volar con la nave de sus sueños, pero parece ser que no funciona.

Thanks to his skill as a helmsman, Rackam navigates the Grandcypher to the mass of dark clouds, where Tiamat is waiting for them. Gran and his comrades must face this great primal beast to save the Port Breeze Archipelago and its guardian deity.

After saving the Port Breeze Archipelago from the threat of Tiamat, Gran and company set off for the Valtz Duchy. Siero introduces them to a Valtz Duchy "special operator," who asks them to search for the missing Archduke Tzaka, the most powerful person in Valtz. They take the job and begin investigating right away, but someone is following them...

Gran and company move on to a secret factory in pursuit of a clue to the missing Archduke Tzaka. Lyria says she hears a voice calling out to her and leads the group to the deepest recesses of the location, where the archduke and an iron giant await.

Gran and company visit another island for supplies, and take on an archaeological exploration job for Siero. The group reaches the ruin's entrance, but a series of events causes them to split up into two groups. Cut off from each other, they move forward in order to meet up again, and encounter the treasure hunters Mary and Karva along the way.

The group makes their way to the Auguste Isles, an island holding an entire ocean. While examining a mysterious substance, Rackam runs into an old friend who leads them to the capital city of Mizarea. There, the group splits up to tend to smaller tasks, while Gran and Lyria venture off to see the sights.

The Auguste Isles are taking fire from the Erste Empire's attack. Gran pursues the abducted Lyria, rushing towards the airship landing site, where the empire's warships have appeared. Meanwhile, Pommern makes off with Lyria, but just then, a primal beast, Leviathan, rises from the sea, along with a gigantic column of water.

Gran and company visit the Lumacie Isles in order to wake up the comatose Lyria. Rosetta leads them to a giant tree nestled deep in a forest. She summons Yggdrasil, the primal beast that protects Lumacie, and explains that with her help Gran can enter Lyria's consciousness.

Lyria returns with Gran and the others to Auguste. They see the city, devastated even more by Leviathan's fury. Eugen is on the verge of giving up when Lyria says, "I want to help Leviathan." At the same time, the skilled knights begin working to protect Auguste.