If I hear a koto, I immediately think of Japan. I have never been to Japan, but the sound of the koto paints vivid images in my imagination of what I perceive to be the finest aspects of Japanese culture. It makes me think of a kind of grace, elegance and tranquility that is seldom experienced in the western hemisphere. Maybe these associations are overly romantic and unrealistic. I don't know. I do know that the koto is a remarkable instrument for being able to evoke these feelings.
The koto is a thirteen string zither with movable frets for tuning. Players usually use three fingers (with finger picks) to pluck the strings. It is a very ancient instrument, being introduced to Japan from China around the eight century. It was developed from the guzheng, one of China's most ancient instruments.
For almost a thousand years, the koto was only played in the royal court. Then, in the seventeenth century, a blind shamisen player learned to play the koto, even though it was against the rules for blind people (or women) to be taught the koto. He composed many important pieces and led the way for other common people to learn this fascinating instrument.
You can achieve a rough approximation of a pentatonic koto tuning on western instruments by using D D# G A A# D. I'll sometimes use this scale when playing the piano or mandolin. The instruments might not be authentic, but you can really hear the oriental influence.
See the video Flowers of Japan, with Koto Music