I don't mind answering what I can. Of course the answers are limited by my actual life :-)

Fluent in Japanese: There is a difference between fluency and proficiency. I am very fluent in Japanese. If I want to say something, I open my mouth and the words come out. If someone is talking to me, I understand what they are saying -- unless I don't, in which case I ask them to explain and then I do. I'm not very proficient in Japanese in that the average 10 year old speaks better than me, understands more, etc, etc. I can read relatively well -- street signs, menus, comic books, novels aimed at junior high school students, and I can struggle through a newspaper if I have to. But (and I'm incredibly ashamed to admit this), I can't write a lick. I used to be able to, but I haven't actually done it in so long that I can barely write my own name. Crazy, isn't it?

Discrimination at work: I currently own my own consulting company and do contracts for foreign companies. I'm currently on a very long term contract with a UK company. When I first came to Japan, I intended only to come for 1 year to learn Japanese (ha ha! one year... so naive). I taught English at a high school. I fell in love with Japan and this area and decided to stay. I taught English for 5 years and it was fantastic (highly recommend it to anyone who has the opportunity).

So the only opportunity I've had for discrimination at work was at the school. Keep in mind that I was on a year to year contract and I was an "Assistant Language Teacher", which means that I was on the bottom rung with no career advancement possible. Nothing to do with where I came from, just you need actual teaching credentials to advance ;-). Also in a public high school (where I was teaching), you need to get your teaching license which is ridiculously hard (basically, you need to know everything that is taught in high school for every subject, and you need to have a university level understanding in your specialised subject). I could easily pass the English tests (even the grammar!) and the interviews, but there is no way I could pass the general test (remember, I can't even write my own name!). So there's a filter there and in the history of Shizuoka prefecture there have only been 2 foreigners who have passed the high school teaching license -- both Chinese (I checked). It's actually a dream of mine to pass the license even though I'm too old now to realistically teach in a high school by the time I could pass.

Having said all that, I worked with some magnificent people and I worked with some horrible people. Now, normally I'm not that judgemental about people, but the school I worked in is very near the bottom of the school system (schools are ranked) and so the worst teachers are sent there to be reformed. This means that you get some real stinkers, but that the principal and vice principal are usually quite good because they have to deal with these horrible teachers. Next step in your career past that school if you are on the way down is to get fired (and that's incredibly hard to do in the school system).

So like I said, I worked with some people who I have to say rank as some of the worst examples of humanity that I have ever met in my life. They were petty, vindictive, mean... Let me just give you an example. One person I worked with hated one of the students. I don't know why. He was a nice guy, but she just hated him for some reason. She tried to get him kicked off of the baseball team. For no reason. Just because she hated him. He complained to the principal and the principal asked everybody in the department (including me) what the deal was. We all said that she's just crazy and so the guy was allowed to stay on the baseball team (and the teacher was lectured -- you have no idea how long... maybe 8-10 hours!) So this poor guy was having a hard time at home and one day his mother threw him off the second floor balcony of their apartment. Luckily he didn't die, but he broke his arm. The school intervened and offered to set up a foster home for him, or if he wanted they would find an apartment for him and set him up with a job with a local company (quitting school). He chose the latter since school wasn't going well for him either. That teacher started crowing the next day how she was right about him and what scum he was since he gave up on school. Complete nutcase.

Anyway long story short... in 5 years of working even with people like that, I was never involved in any discrimination at work. On he contrary, people often complimented me on picking up "the Japanese way" and doing things appropriately. Which is not to say that I've never experienced discrimination in Japan -- I have, but never at work (YMMV, of course). The worst discrimination I've received in Japan were from expats who complained that I enjoyed Japan too much, spoke too much Japanese and hung out with too many Japanese people. "They'll never accept you, you know. You should just be yourself." On the contrary, those people never accepted me and I was being myself. My Japanese friends were perfectly happy for me to be whoever I wanted to be. I had one incident where the husband of a friend of mine refused to speak to me ever. I could never figure out why until my friend said, "I'm sorry. He doesn't like Europeans". Which floored me, but... I know lots of people in Canada and the UK who don't like "brown people", so it was an interesting experience to be on the other side.

Is this a place where I would be happy to be for the rest of my life, to start a family and retire: Yes. Absolutely no question. This is my home. I'm a bit old to be having kids (I'm 50), but I got married here. My wife is Japanese and we met while I was teaching here. My wife's family is amazing and I've had absolutely no problems at all. My mother in law refers to me as her son and often introduces me that way. Sometimes people do a double take, but nobody has ever said anything (they are Japanese after all!).

When I go travelling with my wife, foreigners are supposed to give their passport or foreigner registration card to the hotel so that they can make a photocopy of it. But given that my wife and I speak Japanese together and I'm perfectly at home here, I think most people assume I'm a naturalised citizen. I have an accent when I speak (which people kindly say is not that bad), so it's obvious I'm not from here originally.

Somewhat strangely, I'm not even a permanent resident yet. After I got married, my wife wanted to see what it's like to live in a foreign country, so we went off to the UK for 2 years. That reset my counter. I'm not actually sure when I can apply, but I think I can probably do it soon. Due to British ancestry I can work in the UK, but if I get Japanese citizenship, I'll have to give that up. My wife's mother is getting older (in her 80's) and while it's hard to think about, after she passes away we might go back to the UK for a while. However, when we are done travelling, I will definitely apply for citizenship. In fact, I'm always worried that something will happen, or the rules will change or something like that and it's very tempting to do it now. But yes, this is home for me and hopefully this is where I'll retire.

Hope that rambling account was interesting for you. I've lived in 4 countries in my life: Canada, the US, the UK and Japan. All have advantages and disadvantages. All have challenges. I fit in here better than I fit in anywhere else. Not everybody is like that. Some people (many, many people to be perfectly frank) do not like living here at all. You have to become Japanese if you want to be treated as a Japanese person. If you are not willing to do that, then it can be very difficult to live here long term. However, if you only want to live here for a year or two, then it's no problem at all (and in fact, can be considerably easier).