Just stumbled into this old thread. For anyone else who comes by, there is now an active ACX/LW group in Tokyo, meeting in Nakameguro monthly.
See https://www.lesswrong.com/groups/2Gx38j5JBc4AyHJ9a
Okay I've created a Facebook group here: https://www.facebook.com/groups/LessWrongTokyo/
(To be sure, I don't currently live in Tokyo, but I visit there every summer and would be very interested in attending during that time.)
I'd like to gauge interest in an (english-language) Tokyo area meetup - given Tokyo's size, if a couple people are interested, it would be good to pick a location/day that's convenient for everybody. Otherwise I will announce a date and time and wait in a cafe with a book hoping that somebody will turn up.
I have been to several LW gatherings and have met consistently awesome and nice people, so if any Tokyo lurkers are reading this, I can assure you it's totally worth it to come! Please make yourself heard in the comments if you are interested.