At Kawaguchiko Station, there are two really good restaurants nearby.
One is the Hoto Fudo, just opposite the Station. You can literally see it when you are standing at the station door.
The restaurant served Houtou Fudou, which is a local food in Kawaguchiko. Very tasty and nice. Don’t need to order too big a pot. I think one pot is good enough for two person !
The other restaurant that I can recommend is Fuji Tempura IDATEN. It is about 5 mins walk from the Kawaguchiko station. What you do is walk to the main road (which is the same road as Hoto Fudo) and turn left.. walk about five mins and you can see the restaurant on your left.
No need say, just order the Tempura set 🙂