Tristia, an ocean city that once prospered through maritime trade and was so beautiful it was called a jewel of the sea, has lost its former brilliance to dragon attacks. Its people have tried hard to rebuild, but every attempt has failed and the city has only grown more desolate. Out of hope, they call on Prospero Flanka, a legendary inventor known for reviving cities that would otherwise have been lost. When the long-awaited day finally comes, only a single girl is waiting at the port: Nanoka, the granddaughter Prospero has sent in his place. The two-episode OVA is an adventure with mecha elements.