Whilst not a lawyer Ihave
a) not read past hte frist page of this thread and
b) looked into this a bit.
I can only speak for Australian and US law, so sorry to everyone else.
In Australia and the US there have been examples of charges laid against people for "lolikon", however it doesn't stick that often.
The rulings are not on the fictional ages of the girls, but the ages that they appear to represent. Thus, someone who says "I'm 21!" but looks 12 is still illegal.
An example of this is mentioned in the BBC documentary series "The Dark Side of Porn". An American company had a girl (who was obviosuly legal) say that she was 12 in a porn film. Whilst the company got a slap on the wrist, it was still allowed.
In terms of owning or not owning Katawa Shoujo, you have to ask yourself a couple of questions. Firstly, are you doing anything wrong? If you think you are, then you probably are. However, as most people know, all of the characters are in their last year of highschool. We're not talking about 13-15 year olds, we are talking about maturing students. That is made clear in the story. The artwork as well depicts characters that are "adult-ish". As you can see from Act 1 they certainly aren't supposed to be exciting people who are into little kids.
The other thing that you have to realise is that if you are a normal person, with normal, legal porn, then there is no crime (at least in the countries that I know of). If you are the type of person that collects photos of little girls or boys in swimsuits then you can expect the prosecution to add Katawa Shoujo to their list of evidence. But if you are jsut a normal person, with average tastes, then I can' see there being any issue. In fact, whilst most people would probably think "you sicko" (like most people do) at the concept of KS, I'm sure any criminal investigators will be more interested in the terrabyes of pirated music and videos that you probably have...
Once again, I am not a lawyer. If you are genuinely concerned about the law then bring it up with a qualified lawyer. However I think you'll find that unless you are actually a perveted child molester then you will have nothing to fear.
My Novel - Now available The Zemlya Conspiracy
<Suriko> Crud would be patting Hanako's head
<Suriko> In a non-creepy fatherly way
<NicolArmarfi> crud is trying to dress hanako up like miku and attempting to get her to pose for him in headphones and he burns money