This little teapot tickles me!
Such a cute shape and the somewhat inept paint job makes it all the more charmin.
It is small, just about 3 1/2 inches high and less than 2 1/2" deep.
I wouldn't use it since I assume it is lead-based.
Marked on bottom Made In Japan - a simple typefaced mark w/o embellishment.
I have only ever seen one other piece like this one - a sugar bowl I found whilst doing image searches.