Isu wood comes from a tree that is officially called “Isu no ki”.
Isu no Ki produces a exotic hardwood which can be split into Isu and Sunuke wood and can mainly be found south of Kyushu islands.
This wood is characterized by the fine grains and the warm and charming coloration, which ranges from a light creamy color to the dark chocolate color of Sunuke, gives it a feeling of exquisiteness. Isu is a hard wood, however, due to it’s nature as a young wood, it’s more prone to dents and damage due to impact, which is why it’s not recommended for intense contact practice.
In the last few years, this material has become more and more rare, especially Sunuke which is extremely heavy and hard, and is mostly used to make high quality Bokken. Since it is both relatively hard and heavy, a lot of practitioners use Bokken made of this material for Kata practice in Japan.