A chasen is a traditional tea whisk for making matcha. It uses its fine strands to break up any clumps in the powder to make smooth frothy matcha.
 
How To Care For Your Chasen Whisk:
Do not store it in its plastic container. 
In everyday use, do not wash your chasen with soap. Simply run it under hot water and remove all visible signs of matcha. Pat your chasen dry or let it air dry.