"The soft can counter the hard, the weak can counter the strong. Being soft at the appropriate extent can be a virtue, being inappropriately hard can be a menace. The weak is what the people will help, those that pretend to be strong is what people will resent. Soft, hard, weak and strong, to each has its appropriate place, and one should combining these four and use them where it is most appropriate. When neither the beginning nor end is visible, no one is able to gain full understanding. Heaven and Earth, like the myriad of things, also changes and transform. Thus the commander-in-chief should make changes and not be constant when situation depicts. He should change and transform in response to the enemy.

He does not precede affairs; when the enemy moves, he immediately follow up with it. Thus he is able to formulate inexhaustible strategies and methods of control to secure victory, sustain his gains, bring tranquility and order to the whole land, and settle the Nine Barbarians. Such strategist is a teacher for an emperor."

- Sanryaku (三略) [Three Strategies]

Kosshijutsu (骨指術) is an ancient name for a combat style that focuses on damaging soft tissue and nerves. Other historical names for Kosshijutsu are Shitōjutsu (指頭術) [Methods of using the finger tips] or Hichōjutsu (飛鳥術) [Methods of the Leaping Bird].

The kamae (構) [postures/structure] of kosshijutsu are wide, but can be either deep or shallow depending on the situation. Kosshijutsu uses distance to protect the user from attack and to initiate strikes to soft areas to break down the opponent. This is reflected in the kamae, which aim to keep the user as far from enemy attacks while maintaining attack angles and mobility. This extends to weapons as well, maintaining safe distance, attacking weak points and breaking down the opponent's defences. 

Kosshijutsu waza (技) [techniques] focus on striking nerves and soft areas, or displacing the balance of the opponent. Throws and locks set up the opponent for further strikes and work in synergy together to break down the opponent. Safety is a foremost concern in kosshijutsu, so waza are usually engaged in such a way that the opponent cannot retaliate. Strikes, throws, locks and other attacks all target weak points or set up the body to take advantage of a weak point. This extends to weapons as well.

The jutsu (術) [methods] follow along the same general idea as the kamae and waza. Drawing the opponent in, waiting for them to over-extend, then striking at a weak point. Letting the opponent flow in, then cutting off that flow. 

The kata (型) [forms] vary in length, but are usually made up of three to five waza and two to three jutsu. Attacks are done with distance in mind and defence is achieved by creating openings for the opponent to exploit, then turning the tables by striking to a weak point (muscle, joint or nerve). 

Kosshijutsu and Koppōjutsu are two sides of the same coin. Kosshijutsu is wide and open, Koppōjutsu is close and compact. Kosshijutsu creates openings to invite attack and counter, Koppōjutsu creates openings through misdirection to attack from different angles. These two systems have different approaches to engaging an opponent, but together they create a strong blend that is unstoppable in the right hands.