Well here's what I did. The first time I went through and played the game, I couldn't beat Grand Theft Auto for Kenji so I killed him and finished the game without 100%. The second go around, I tried and tried on kenji and finally did the mission. So my advice is do whatever you want to if you plan to go a second time. If not and you want 100% on your 1 and only go around, then you definitely have to do Kenji's missions. but you still advance to ssv if you kill kenji before finishing him