The trick is as follows: They fabricate a story that Banemon is going to buy out Koman for 100 ryo, and they are going to make Gengobe, who would not want to lose Koman, believe the story and make him pay 100 ryo.
伴右衛門が百両で小万を身請けする話をでっち上げ、小万を惜しむ源五兵衛から百両を引き出そうという算段である。