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.)
Chat with our AI personalities
Once you become a ninja you get a ninja mask and gain entrance to the ninja hideout. Once you are at the ninja hideout you can buy ninja clothing and furniture, train to become a fire ninja or a water ninja. Or just play other ninjas in regular card-jitsu.
you have to play it to become a ninja. that is where you get the colors.
Well you have to be a member, first of all, then buy that ninja suit, and then take everything off except that and your ninja mask and dance. then you will turn invisible!
You go to sensai and beat him to become a ninja!
To get to the secret dojo, you have to be a black belt, challenge sensei (beat him), and you will become a ninja. Once you beat him he will give you a ninja mask and tell you where the secret dojo is.