The Kai Highway is a location in Mystical Ninja Starring Goemon. It is a large field area situated between Oedo Town and Mt. Fuji. It has a coffee shop and features standard enemies, like ball dolls and flying wolves. A Silver Fortune Doll is also in this area, lying to the right of the gate to Mt Fuji. A river flows through the area, of which two bridges cross to access different areas.

The area is actually the first area of the game which can be accessed after starting in Oedo Town. The Map of Japan is obtained at the coffee shop, which allows Goemon to view the areas he has already visited. Once the Chain Pipe has been obtained, this area serves no other purpose.