A zaisu (座椅子) is a Japanese chair with no legs but a normal chair back. They are often found in traditional rooms with tatami mats, and are often used for relaxing under heated kotatsu tables. Traditionally, the correct sitting style in Japan is seiza, kneeling with the weight on top of the lower legs, which are folded underneath the body. However this can become painful after long periods of time or for people who are not used to it, so many prefer the zaisu, where the back is supported and legs can be positioned more comfortably. Wikimedia Commons has media related to Zaisu chairs.