This was a book I purchased for my elementary school library in the mid 90’s through early 2000’s.  I think it was published in 94 or 95.  It was a slender black hardcover book with white lettering (I think) about 21.6 cm x 16.5 cm.  I don’t remember a cover image but if there was one it was a simple line drawing.

I think one or more of the keywords Japan, Japanese, stories, koans, or zen were in the title or prologue.  It had brief stories (one page or less).

Here are two I remember:
*The master pours tea in a student’s cup, but the cup is full so what the master poured spills over the sides.
*The master and student are walking down a muddy road.  They encounter a woman standing before a muddy muddle.  The master carries the woman to the other side of the puddle, puts her down, and he and the student trudged on.  After many minutes the student blurts (something like) “Master why did you carry that woman?  You know (avoiding women?) is part of our practice. The master replied that he carried the woman but a few steps but the student was still carrying her.
I’ve scrolled through what seems like millions of hits for Zen and koans with no luck. It was written for young people (5th-adult?) according to my search tools.  It was not in a picture book format like the Muth books. And it pre-dates them by many years.