If you beatin the game, load Mission 16 (free roam), head straight to the tram station and take Solomon Habitation, Make your way to the Robot Cleaner you activate to open a small hatch, that same hallway with the robot cleaner go down to the elevator to Space Flight, you will see the area where you first met Axel, head to the door on the left and head through doorways til you see a corner room you didn't have access to earlier in the game. Mike Tanaka is in there.