The book is probably from his master's mistress. The master has katana and sea dragons are usually eastern.. also its suspicious that Leon is not yet allowed to meet the family of the mistress and his master seems to tolerate dragons even tho he is was a dragon slayer. Maybe I'm wrong kek.
Master's wife maybe? Consider he doesn't seem that surprised that Leon got together with Roseweisse..
No this book was written by leon mistress sister
Off-the-cuff hypothesis: The Imperial and Sea Dragon Royal Families are one and the same.
The book is probably from his master's mistress. The master has katana and sea dragons are usually eastern.. also its suspicious that Leon is not yet allowed to meet the family of the mistress and his master seems to tolerate dragons even tho he is was a dragon slayer. Maybe I'm wrong kek.