When the Fuma-clan fought a fierce battle against the Koshu-clan known as the “Koshu-Toppa”, the Koshu clan planted spies in the Fuma-clan. Just after the Fuma-clan broke out from Kousyu, their boss Fuma Kotaro gathered all his members on a river and Kotaro made them sit down right there. Kotaro shouted Fuma's secret question while swinging a torch so abruptly everyone stood up. The Koshu clansman who did not know the answer were slayed right away. This was both a simple and effective way to distinguish their enemies and real members immediately.