What I ment was that Sanosuke doesn't really act his age, he's 19-20 and he acts and thinks like a kid at times.
"And you still act like you're in Freshman year
What the hell is wrong with me?
My friends say I should act my age
What's my age again?"
"No one should take themselves so seriously
With many years ahead to fall in line
Why would you wish that on me?
I never want to act my age
What's my age again?"
But I understand how it doesn't suit him perfectly (maybe it's just my wierd way of thinking

) but there was this other song:
Simple Plan - Grow Up
"I don't wanna be told to grow up
and i don't wanna change
i just wanna have fun"
Maybe this one's better.
The one who walks among the shadows of the living and the dead. - Flame the Alley Cat