Kaio-Ken is primarliy a powerup move taught by King Kai in the Next Dimension, it is a strong technique but takes quite a bit out of the user and can even destroy him/or her.
What happens when you go Kaio-Ken?
Well first off, going Kaio-Ken gives you a boost to your Power and Speed, allowing you to better combat your enemies for a short period of time. However, using anything more than Kaio-Ken X1 puts GREAT strain on your stamina and body.
How do I go Kao-Ken?
Well first of all you need to have learned the ability from King Kai himself (yes that means you must be dead). You need to at least have a power level of 500 to learn Basic Kao-Ken and have gone through all of KK's training.
How do I increase my Kao-Ken Level?
First off, you must train in a gravity simulator purchaseable in the item shop. You can only learn 1 kaioken level per day, and per grav sim. The time required to learn kaioken is dcided by the level. If you have lv1, it takes 1 training period (5 minutes). If you have Lv12, it takes 1 hour and so on.
Kao Ken X1 adds +100D,+50SP,takes 100KI
Kao Ken X2 adds +200D,+100SP,takes 200KI
Kao Ken X3 adds +300D,+150SP,takes 300KI
Kao Ken X4 adds +400D,+200SP,takes 400KI
Kao Ken X5 adds +500D,+250SP,takes 500KI
Kao Ken X6 adds +600D,+300SP,takes 600KI
Kao Ken X7 adds +700D,+350SP,takes 700KI
Kao Ken X8 adds +800D,+400SP,takes 800KI
Kao Ken X9 adds +900D,+450SP,takes 900KI
Kao Ken X10 adds +1000D,+500SP,takes 1000KI
Kao Ken X11 adds +1200D,+550SP,takes 1100KI
Kao Ken X12 adds +1400D,+600SP,takes 1200KI
Kao Ken X13 adds +1600D,+650SP,takes 1300KI
Kao Ken X14 adds +1800D,+700SP,takes 1400KI
Kao Ken X15 adds +2000D,+750SP,takes 1500KI
The list continues like so until lv 20 of Kaioken