Japanese Keshi Pearls: Japanese Keshi pearls are the closest pearls to the olden natural pearl, Known as the basara pearls, that you will ever encounter. The difference of Japanese keshi pearls and the Natural pearls are that the natural pearls are formed in the wild while the Japanese keshi pearls are natural pearls formed in controlled environments. Both are Composed entirely of nacre. Akoya keshi are found primarily in the Sea of Japan and are a natural seawater pearl. Japanese Keshi Pearls are made from layers of nacre but in this 95% nacre and 5% tissue are present.