MASA Nagashima from Saitama serves plain dogs, hokkai dogs (with tomato sauce), and chilli dogs (with homemade chilli sauce) from 8.30am-6.00pm everyday. He also sells spicy fried Hokkaido potatoes.
Masa-san travelled all over the USA last summer and collected licence plates from 50 states. You can see them on display on the inside of his brandnew Hokkai Dog van parked across from Hirafu-tei on Hirafu-zaka.