(1) It is one of the costumes worn under an outfit. It refers to a katabira (light hemp garment) worn in to get rid of sweat. It is also known as asetori, a cloth used to soak up sweat. Its shape was exactly similar as hitoe (a single layer of kimono) and was small and short. It differed from hitoe with its use of hemp cloth. It was worn over the hitoe only during summer in medieval times as the name suggests, but it was later worn throughout the seasons to wear a kimono properly not to allow it to come loose, and aka-katabira (red light hemp garment) was worn during summer while shiro-katabira (white light hemp garment) was worn during winter. Color used from long ago ranged from shiro (white), moegi (yellowish green), ko (yellowish light red), ai (indigo) ("Gyokuyo" [Diary of FUJIWARA no Kanezane]), zuri, kurenai (crimson), aka (red) ("Sankaiki"[Diary of Tadachika NAKAYAMA]), and asagi (light yellow) ("Makura no soshi" [the Pillow Book] and "Tamagusuri" [Gunpowder]).
(2) It was a robe worn by buke (samurai family members) below hitatare (a kind of court dress in old days) of hitoe made with a white cloth crisply starched. It was used in formal occasions in order to dress neatly. Regarding its appearance, it had an end sleeve without an okumi (a kind of gusset, a long rectangular cloth sewn onto the front side of a kimono) and had a similar shape as hitatare without a breast cord.
(3) From the Kuge (court noble) Muromachi period, instead of hitoe, akome (inner wear) and shitagasane (long inner robe), the okatabira was worn with the sleeves of shitagasane attached or with the sleeves of hitoe sewn on as the end sleeves, disguising as if the okatabira, shitagasane and hitoe were all worn properly. Its shape lacked okumi and had the end sleeves taken from the sleeves of hitoe as mentioned earlier, having a similar shape as the okatabira of the buke in (2), thus having possibly been derived from it. Since hitoe do not have end sleeves, okatabira are longer in the sleeves than hitoe.
The oldest extant okatabira is from the late Muromachi period and owned by Uesugi-jinja Shrine, but its shape did not differ from the early modern one. Hayashibara Museum of Art has an okatabira from the early Edo period.
In addition, at Kamo Festival this okatabira had used until recently, but nowadays an okatabira with the same yuki (distance from the seam in the back of a kimono to the end of the sleeve) as hitoe is used.