This character wears a happi.
Happi is a traditional Japanese straight-sleeved coat usually made of indigo or brown cotton and imprinted with a distinctive mon (crest). They are usually worn only to festivals. Originally, these represented the crest of a family, as happi were worn by house servants. Later, the coats commonly began to display the crests of shops and organisations. Firefighters in the past also used to wear happi; the symbol on their backs referred to the group with which they were associated. In English, "happi" is most often translated as "happi coat" or "happy coat".
Traditional Japanese Straight-Sleeved Coat