Hosokawa Tadaoki
Tadamasa sent a spy to Kokura to try to observe the fortification. Spies examined Kokura Castle from the sea. The castle stood by the sea. One night, light leaked out from the spies' ship, revealing their location to the castle. Taken into the castle, lord Hosokawa Tadaoki (細川忠興), heard their story and forgave them and gave them the castle blueprint and released them. Tadamasa constructed Tsuyama Castle by referencing the blueprints.