Modern Chinese 60cc engine in Japan in an older style bike. Edit: the frame and tank appear to be a German Rex and this makes the third one I've found in Japan in one day. The question is whether some Rex bikes, or engine and fork kits were exported to Japan. It's probably unanswerable now.
A Chinese bike with a Chinese engine. Picture by a Japanese in China for some reason.
This was posted before but it disappeared/expired.
Late 1950s Baby Climber, in 50/60/75cc versions
Early 1950s, I think. Toyo