16. Ko-uchi-gaeshi 小内返

Ko-uchi-gaeshi 小内返

Small Inner Reap Counter

Classification: Te-waza (Hand Technique)
Japanese meaning:

Ko = small
Uchi = inner
Gaeshi = reversal or counter

This technique is a classic counter to ko-uchi-gari, taking advantage of your opponent’s committed attack and using it against them.

Technical Description

When uke attempts a ko-uchi-gari (small inner reap) on your right leg, tori responds by sliding the attacked leg backward, avoiding the reap. As uke becomes temporarily unbalanced and focused on the failed attack, tori immediately rotates the upper body to the left, using both hands to guide uke into a fall.

Instead of resisting the technique, tori allows the energy of uke’s movement to continue, but redirects it in a circular motion, resulting in a clean forward throw.

This throw embodies the judo principle of “sen no sen”—intercepting and countering at the exact moment of attack.

Biomechanics of Ko-uchi-gaeshi

This technique functions as a moment throw:

F1 and F2 (the arms) generate rotational torque, extending the force initiated by uke’s attempted reap.
Re (reaction force): Tori lets the attacking leg move freely, then initiates a swift upper body turn to extend the momentum.
There is no real blocking or lifting—only a redirection through timing and rotation.

Much like Sumi-otoshi, this is a downward arm throw, driven by forward pressure and precise redirection of force. The main biomechanical action is done by the hands, not the legs.

Did You Know?

Ko-uchi-gaeshi is a beautiful demonstration of kaeshi-waza—using the attacker’s own energy against them.
It is a high-percentage counter used in competitive judo, especially against opponents who rely heavily on ko-uchi-gari.
The name gaeshi appears in many reversal techniques (uchi-mata-gaeshi, sasae-gaeshi, etc.), and always signifies a turning of the tables.
This technique requires excellent timing and awareness of rhythm in randori.