As soon as government started going out of control, hunting down imPorts and forcing them to register, Kiryu was more than ready to go underground and disappear. He certainly wasn't about to play that game again. This place was his escape from that sort of thing back home and he was determined to make it stay that way.
Needless to say, it didn't work all to well. He'd made a point not to mention his powers directly over the comm, not necessarily because something like this could happen but it was certainly a good reason, so he wasn't high-priority enough to go after right away. And he was able to stay hidden for about a year before he ended up getting arrested for shoplifting and discovered. The officials forced him to register and kept him in custody for considerably longer than usual for shoplifters.
It wasn't the last arrest. He never got arrested for anything too extreme--he made sure not to get blamed for anything rash he did do, as annoying as that was--but each time he got held for longer. The government knew he had some sort of dangerous power, but they couldn't prove it--he was completely powerless in his normal form, after all. After the fourth arrest, he finally decided enough was enough.
About three years ago, with help probably, he staged his own death, made sure it was seen, and became Okita Souji, whose probable powers had never surfaced. As hard as it was to give up defying the government directly, he convinced himself that even just living under their noses would good enough for now.
He's pretty much been just living for the past few years. He and his friends haven't appeared to be a threat so they're left alone. He still goes to visit his "grave" every year (
like so). He's been to Peru a couple more times too.
One thing he refused to do was dye his hair. He got a couple wigs instead. Unfortunately, he can't wear contacts, so he can't hide his eye color, but he can hide everything else.
He can usually be found playing an instrument or demonstrating kenjutsu on a street corner, or hanging out in central park with his
completely innocent looking dog.