Online- join us on the Diamond Hands telegram group and that's where most serious bitcoiners are. (English speakers are also welcome)

https://t.me/+HDKHKkjJNwo1Njk1

Offline- Diamond Hands also organizes some meetups and events occasionally. Also Tokyo Bitcoin Hackers aka Tokyo Bitdevs host more technical meetups for English speakers.

Fulgur Japan also recently announced a physical "Bitcoin hub" in Tokyo and it actually looks amazing. I think this will be the go-to physical place for both local and international bitcoiners to meet in the future. I'm pretty excited about the hub as well.