When a warrior trains another warrior..

[Kazuya]

That's Sensei. And yeah, you have to be in the same alliance, and your base ki has to be at least 500,000 above the other's.

-Kouhai -You can only train someone in your alliance that is weaker then you by more then 500,000 Ki. You can give him a portion of your own Training Points in return that he becomes your Kouhai(student) and has to obey your orders since you are his Master/Sensei. Note that you have to activate this each time before Training Points are given out on Sunday. So you can change it during the week. If you have the Teacher ability, the efficiency by which you can train others is better.