The ear drilling device also reads Kaiji's body temperature and pulse. Tonegawa reads this through his watch. Tonegawa uses this as a lie detector to tell when Kaiji is dealing slave/emperor. Kaiji later cuts off his ear in the bathroom to remove this device and wins against Tonegaway with by betting 20cm (this would be fatal if he lost as at this point the drill is 1cm away from his eardrum)
As punishment for losing, Tonegawa is forced to prostrate himself on a giant frying pan (hands, and face) for 10 seconds.