I adore Jin. As tough and cold as he can be, I love that the series shows flashes where it's quite obvious that he IS only 21. Anime generally has a healthy disregard to age and maturity level for said age (as in Sanzo being irrationally curmudgeonly for 23), but in SC you remember that for all his ability and stoicism, Jin is really quite young. It's why he's so obviously conflicted when it comes to the prostitute he falls for and why he does just as stupid stuff as Mugen sometimes. I could go into a huge character study of Jin (and probably will sometime in the future).

There's an amazing fight at the end of the series where Mugen and Jin are fighting together and you get to see that because their styles are so different, they compliment each other perfectly.