As described in 『The school』page, the founder invented Kappougi and it spread out through the country. But what is Kappougi anyway? 

How famous ?

Kappougi(割烹着) is Japanese Apron smock is used particularly when cooking or cleaning. This has baggy sleeves with gathered cuffs terminating just after the elbow, and the torso comes down to the wearer's knees.[1] It closes by means of strips of cloth that are tied at the back of the neck and waist.