|"Folded metal is only so strong. The monks of the far hills used ancient supernatural skills to turn Hiryu into something special. Its secret died with them.."
In game weapon description..
The Katana Hiryu is a Legendary Weapon in Fable and Fable: The Lost Chapters. The only way to aquire it is by completing the quests to marry Lady Grey. If it succeeds, Hero and Lady get married and now Hero will have access to Bowerstone Manor. In it, it is located in a 15 key chest in Lady Grey's bedroom.