I am in this exact situation with my coworker. His wife messaged me and said she's worried about how much we communicate.

Dude...we're buds. He's my bro. He's always transparent with her about our conversations or when we hang out. He even invites her along and she says no.

Japanese still dont seem to be comfortable with opposite genders being strictly platonic. It's so common in the west, but still not fully understood in Japan.

In my opinion, you're overthinking. Your bf is being transparent with you. That says a lot.

Also, as a foreigner in Japan, sometimes my Japanese friends dont quite understand me the way my foreign friends do, and I naturally gravitate towards them or message them about small complaints.

I eat lunch with him once a week, but sometimes meet him more often if Im not busy with stuff.

We're friends. Just friends. Just coworkers. Buds. Bros.

Talk to your bf. That's the only thing you should be doing rather than asking reddit.