Means the Fist of Killing, the practitioners of these beliefs believe that killing the opponent is the way to use their martial arts skills. It is the yin belief that martial arts were created to kill and destroy. There are also those who walk this path for revenge, hoping to kill a certain person instead of just using their martial arts to kill.
Yami and Yomi embodies this principle and recognizes that it cannot prove that Satsujinken is the true meaning of martial arts without defeating Ryōzanpaku, who embodies the principle of Katsujin-ken and the Strongest group of masters. In practicality, it seems that practitioners of Satsujinken have the advantage over Katsujinken, as they do not need to hold back while fighting.
The yin belief that generally bare-handed martial arts were created to kill and destroy. The general term (for both bare-handed and weapon based martial arts) is Satsujindo. Despite this a follower is not obliged to kill an opponent. Yami embodies this principle and recognizes that it cannot prove that satsujin-ken is the true meaning of martial arts without defeating Ryōzanpaku, who embodies the principle of katsujin-ken.