oh, Japan - interesting. Are the friends all Japanese, or are they ex-pats like you?
I live in a very conservative part of the U.S. where women do not seem to bring up boobs much - I've had some discussions with my sister about our boobs, and even pre-transition I've had discussions with a particularly open friend about boobs and nudism / naturism - but I've never had a woman ask to touch my boobs or offer for me to feel their boobs 😅
I'm pretty insecure about my boobs, they are small for my frame (though maybe larger than a lot of trans girls I know, women in my family tend to be large; a trans girl friend of mine has indicated she wishes she had more boobs after seeing me).