Jiyu-kumite refers to the practice of using all the techniques you have learned until now against an opponent. You cannot be off your guard even a second. This is a very serious training method. If you do it for enjoyment, you can get injured. Jiyu-kumite is not designed for deciding victory or defeat. It is the practice of offense and defense with the development of the techniques. You can not improve if you always think about victory. As a matter of fact, you should not excite (or stimulate) your opponent more than needed when you practice kumite. You have to respect any opponent you have when you practice. In kumite, it is forbidden to attack your opponent with direct contact. As a principle, any technique you use will have to be stopped before it connects. However, when you are in defense, you have to practice as if you are actually being attacked. Any injuries in kumite are usually because of carelessness. Especially common is the injury of fingers when the fist is opened. The fist needs to be firmly closed. Practicing using an open hand should be restricted until you improve enough.
There are eight kyo (opportunities) to take advantage of when you attack:
- Right before the opponent changes to the next movement.
- Right after the opponent has made a movement that was not effective.
- When the opponent lacks harmony between the techniques used and his mind, during both attack and defense.
- When the opponent's mind is dispersed and is not really ready.
- When the opponent loses his balance when he makes a movement.
- Right before the opponent breathes in deeply.
- When the opponent is confused because of your movement.
- When the opponent is daunted by your tactics or ability.
The five unguarded moments you have to prevent when you are in defense:
- The unguarded moment in the mind.
- The unguarded moment in the spirit.
- The unguarded moment in the technique.
- The unguarded moment in the appearance.
- The unguarded moment in the act. (The same as in normal life, if you behave badly, you have to take responsibility for your actions.) If you use techniques that do not follow the rule, that is faulty. ' 
Click here for the rules of Goju-kai Tournament Jiyu Kumite