To earn this, you must go to Nam Cobanda Island with the books that the Kow wants. The books are as follows (as well as their locations).
~Halure's Mayor's House
~Fortune Market HQ at Torim Harbor
~Knight's HQ in Heliord
~Flynn's House in Aurnion.
The answers are September 30, 1998, Raine, Bubbles, Presea and the option about turning to stone.
*Note that Nam Cobanda Island is unlocked after the Castle appears in the sky*