An early Edo period document stipulating the Hosokawa clan code of conduct for vassals dispatched on a national project to rebuild Sunpu Castle has been discovered by Kumamoto University researchers. The thirteen articles from the head of the Hosokawa clan in the Kokura domain (area), Tadaoki Hosokawa at the time, delegate full authority to the vassals to lead construction and prevent conflicts with other clans. It is the second original code of conduct document related to the Sunpu Castle reconstruction effort to be discovered.