Stranded in Japan without shoes?
Big sized men's shoes found!
According to the American Academy of Orthopedic Surgeons the global average shoe size for an adult male is US size 9 - 12. As hard as it may be to believe the largest size footwear carried for men in most Japanese shoe stores is a mere 28 cm (around US size 8 1/2, EU size 43), and even if you are looking for 28 cm shoes you will likely find the store will only have a couple styles to choose from.
If you're in Tokyo, the good news is the "big-b" shoe store, conveniently located in Gotanda, on the Yamanote train line and has big sizes, really big sizes (US 10 - 18). And if you have a wide foot, no problem they got the widths too. They also have a reasonable selection of name brands and styles.
big-b's is not inexpensive, but they don't gouge you either. As far as I could tell the staff do not speak English, but they certainly are very helpful and language shouldn't be much of a barrier for non-Japanese speakers.
How to get there: Go out the West exit of JR Gotanda Station, make a right and walk down the road running right beside the Yamanote train tracks for about 250 meters (the tracks should be on your right).