Piro's rant explains why the knee brace is there.
Anybody looking to speak out in favor of a Piro/Yuki relationship? Don't.

Piro speaks:
er... it's not exaclty socially acceptable in japan either, dude. Your opinions are fine, but stating that japanese culture has no problems with relationships with underaged girls is wrong. In fact, a big selling point for ATMs in Japan is that some actually 'wash' the money - so girls can feel better about not touching money that was handled by 'dirty old men'
Besides - Seraphim represents what deep inside piro HIMSELF feels is morally right and wrong. Since he's an american, you are partly right. Despite the fact that she DOES get other jobs occasionally, she really isnt privy to outside information (for instance, she is not going to spy on Kimiko and give piro some pointers on how to date her) She can only react to piro's feelings and what he himself knows.
Deep down inside, it's Piro himself that feels that attraction to girls much younger than him is wrong. If he didnt, his 'concience' wouldn't be scolding him about it. A lot of anime fans hum and haw over the fact that these girls that are presented in anime as being 15 tend to look and act a heck of a lot older. This is probably because the target audience of most of these shows are kids in that age group, and *they* fantasize about growing up.
All of this is really a moot point as far as where the story will go - people have ways of self-justifying thier actions, wright or wrong. I could care less about the legal ramifications of Piro dating a 15 year old. i have seen so many threads on the subject that its just getting annoying. So it's legal in japan - who cares? You think the first thing that would happen if Piro hit on Yuki was that a friggin swat team would decend on him? --;; Maybe the biggest problem he would have is that the relationship wouldn't work and both of them would get hurt. Or would they? Maybe Yuki is more mature that Kimiko is, and in truth would make a better match for piro? Or maybe Piro finds that he develops a crush on Erika - opposites attract, you realize (it would be more true to the relationship between Seraphim and myself in real life, if you must know). Maybe Piro doesnt hit it off with any of them? There is also the possibility that piro might hit it off with M... er, the 'Darkly Cute' girl. Does he really know ANYTHING about any of them, really?
The truth is, it's hard finding a meaningful relationship in life. Weak relationships dont last. Strong ones are hard to find. Maturity is not nessisarily important in life - it comes at different ages for different people, and sometimes never comes at all.
I'd rather let the story float along a little more before i talk more about the tangles in all of this.