We propose a cat tail device that can indicate intentions and emotions, do self-expressions suchas cosplay, and extend human body. String drive can move the tail elastic like an animal, and suitable for wearing device due to it’s lightness. However, long and narrow things twist when driven by string, and cannot move the tail as expected. To resolve this problem, we cover tail core (made by cotton bag) with a mesh tube which is flexible but uneasily to twist. By this mechanism, we realized wearable robot which is light and make S-shape like a cat tail.