Fire King restaurant ware mug

Fire King has been popular in Japan especially for these five years.
Almost all items are quite expensive if you buy Fire King in Japan and I can't afford to buy them.

Unfortunately, I don't think that the tableware I have in my place and Fire King go together very well, but I spotted this small mug at an antique shop in the U.S. and bought it because it was in a good condition and very cheap.
It had been used as restaurant ware and it is smaller than regular Fire King mugs.

My husband has been using it as a toothblush mug.
I have been looking for the same one in a good condition, but I haven't found yet.