I think most people stress the BMI on here because it is the one thing that you can check yourself before you go. It would be a waste of time and a little embarassing to go to the medical then get sent home for being over the BMI. As to why the Japanese care about it? I have no idea. It is what it is and as I have learned, dont ask or try to understand. I wouldnt worry about the smoking at all as long as you are in good health.
Yes, i am 26. I got lucky and everything fell together when I was younger. I wont bore you with the details...