When you go into the juggernaut you have to fight prince cort exactly 100 times in a row then for the 101 time songi would stop you and start fighting you. After you beat him there would be a subtitle saying i heard what you said songi now i am going to kill you! from cort. Now songi would only be in your team when you fight cort, after you beat cort songi for the 101 time then he would replace or if you don't want to be in your team and he would be at level 50 once you get him. Once you have him you will be the strongest fighters in the world you can also bring him to the musle dome!