It's actually a reference to One Tree Hill
*listens to retching in the background*
*continues*
It represents, at least to me, the struggle between self and society, to fit into society while still defining oneself as an individual, and the struggle between childhood and adulthood. I think they both last for your entire life, and a lot of people give up on it (both individuality and childhood), so it's also a reminder that I'm not just what everyone wants me to be and I can always find pleasure in the simple things in life rather than being entirely devoted to a job and the pursuit of money.
And it will always be a reminder of who I used to be (who I am now), and I like that person, and I think he's a good guy, and I'd prefer not to lose him.
By joining the masses, you ARE becoming one of them, hence 'joining'.
If you're going to do something to permantly alter your body, you should really think of something of your own design, and nothing you see on tv or in other areas of media, but thats just my opinion.
I literally have 6 people in my lecture class alone that have some type of kanji on their body.