firstly, I have never been to Japan,
when I travel around, sometimes people just come up and chat, sometimes it is a guy, and sometimes it is a girl, it only starts as a chat, I have been in a bar and sat down, and chatted to the person next to me, you do not have to chat to them in a lets get in bed manor, it can be as simple as it is bad weather out there, act like a pratt nobody will talk to you, I do not know the places that you frequent, I hope I never find myself in there.