Rui is a green Rooey and Shirobon's partner and friend- they share a very close bond with each other. Rui generally resides (as well as works) at the ramen shop. Shirobon occasionally rides on Rui to deliver noodles to customers. When they're not working at the noodle shop, Rui watches Shirobon train. Shirobon and Rui can be quite competitive when playing an actual game of Bomberman.
[Source: Bomberman Wiki]