Well, you can't really play AS him. There are two face camo items called Raiden A and Raiden B that you can acquire that make you look like him, though.
Chat with our AI personalities
First kill kim. when he's on the ground, take out your syringe and stand next to his head. When he gets up, CQC him, then press triangle. Then Raiden will kill him for you :)
During the SOP (Sons of the Patriots), Olga stated to Raiden that the life of her child (Later on known as Sunny) depended on his own. It is known that after SOP, Raiden had complications with his girlfriend of the time; Rose. After Rose had told Raiden his child (that she admitted she was carrying at Arsenal Gear in MGS2) was miscarried. Through hearing this and the fact that Rose and the Colonel had gotten married, Raiden left to Alaska where the Patriots found him and severed his head.His arrival in MGS4 surely shocked Solid Snake and everyone else as well, as they had thought he too had died and was dead for good. Raiden's head-severing was just the start of him becoming a cyborg ninja.(This also explains why he wanted to protect Sunny so much.)
Assuming he was 21 at the start of the SOP in MGS2 and four years had passed to MGS4, he would've been 25 at that time. Now, after it being five years after Guns of the Patriots, he would be 30, which fits his physical appearance. But nothing is truly known.
you dont
It seems to show that in a life-threatening situation, as Raiden was about to be killed, Rose was the last thing on his mind, which really speaks of his feelings for her. This is also shown by the voice-over of Raiden and Rose's conversation about the time they first met that was played as Raiden was being crushed.