To the casual observer, this cup and saucer set seems like a great little bedside water glass. In Japan, a cup set like this is used to enjoy hirezake, a specialty hot sake cocktail that invoves the fire roasted fin of the poisonous fugu fish. Apparently, it's very, very tasty. This short video gives you a better idea of how it's prepared.
It's up to you how you choose to use this one.
Measures 3.5" x 2.6" cup; 3.2" saucer.