call 119 !
If you need to call ambulance in Japan remember you dial 119.
You can call from your mobile but you need to explain where you are.
The Japanese government recommend try to call from public pay phone.
If you can't find pay phone near by, try to explain where is the landmark near you or go to the shop or restaurants near by and they can call you an behalf.
I hope this information is useful.
yukorose
Japan