I did a stint in Japan in 2004
It's probably changed a lot. The school I was with was below JET and Nova (who had the most ugly, uncute mascot ever). I taught kids aged 2 and 3/4s (I'm not kidding) to retirement classes, evening adult classes, anxious teens/kids who didn't speak for the entire hour, etc.
It is true if you have no seriousness about teaching you have no place, I certainly did not feel in any sort of place though. Teaching was something I didn't know much about and wanted to give it a shot, to see if it was my path. I decided it was a good experience (and has really helped me with my art workshops), and though I can I didn't find it enjoyable enough to throw myself into, largely due to depression, homesickness, lack of resources, illness etc. Kudos to all who go full-on to teach!!
It is now probably a cool way to spend 12 months if you decide to go, and you can choose whether or not to hang around with partygoers or not. With the net we are all better connected to be able to find people we are more likely to get on with, with similar interests of course (look at these boards!). ^_^
All you needed as a degree to go over to teach. Angry with the job market (and non-existent art postgrad "job market" [pffrt]), in '04 I was accepted with haste and flew over. We had little resources available to teach and it was before broadband was accessible in apartments for us, so all my time was spent feeling homesick in manga cafés instead of researching and printing helpful materials for the students. I was able to draw cute pics for the kids as encouragement at least. And I did remember wondering why SO many of the ELTs did not know anything of anime or manga. One or two of them had heard if it at least! But it was very naiive way of me thinking - though I knew it wouldn't be everybody, I did expect a little more than a minority - it was a bit Peepo Choo (read below, R to L).
A small percentage of me knew this was going to happen, but I did not want to acknowledge it; my parents especially knew but you can't tell somebody that, they have to "get it" for themselves, right? I also broke up from a longterm relationship, far away from family and friends. Dating went dreadfully. Lonely times.
In the end I got incredibly ill and had to break my contract and come home, when I basically contracted walking pneumonia from a viral infection. It pretty much screwed up my immune system from there and I live with that consequence every day now, it will never go away. Nobody ever tells you how ill you will get as a Westerner living in Japan, there are now a few YouTube videos of ELTs suffering illnesses a lot too. Of course it is all random, but even if you are subjected to it all, there is no way of preventing it! The medicines are rubbish!
After feeling insanely embittered about the whole experience for ages I figured out what I learnt from the experience;
(1) It was my "levelling up" from early 20yo graduate otaku into someone who felt again a bit outcast about being otaku. Now I realise it was because the moé boom had started and anime/manga was being made differently to our 70s-80s-90s favourites, not that I was a failure at being a fan for not liking too much current anime! I felt despondent for ages, but just threw myself into drawing my own thing. After a small time of doubt regards art style, it's sort of "come back" again, the style I grew up with, so feel more content. It took a long time though :/
(2) On a slight tangent, but also kinda related, I could see the horrible "crying girls who look about 10yo, dressed up in maid outfits hovering over Akihabara" as exactly that; the whole "no no stop it" negative sexualisation of females in hentai was feeling creepier and creepier (there is great hentai out there, Slut Girl by Itsutoshi via Eros Comics is a super example of hilarious, adult fun sexytimes!). It has affected my opinion of moé for a very long time. There is a place in Akihabara where people sell pics of kids (identities hidden by a black bar over their eyes) in vests and pants running around. Why hasn't this been closed down yet? It was in a building that sells lots of cool old CDs. I went to the wrong floor by accident and was hastily shoo'ed away. :/ So that was major yuck, and I just felt like a third class citizen as an ELT. Second class as a woman. My personal experience - I didn't have great experiences as a then-blonde, blue-eyed western female. I was mistaken for a prostitute on more than one occasion walking the short distance home from Karaoke. I was dressed super-plainly.
(3) Even though I felt I was a rubbish teacher, a few of my young students found me on Facebook. They had been living abroad in the US and studied English. I'd like to think I had a tiny part in that encouragement. It was fun connecting with a few of the good kids who wanted to learn as well as have fun.
I still miss the food. The delicious, delicious food. And combinis.
I have visited three times overall; two holidays and once to live. Would always go back again for a holiday; would never go there to live again, though.