Shiro Shozoku (白装束)
Shiro Shozoku means white clothing in the broad sense. It also means being dressed in white from head to toe. In a more limited sense, it means hitoe (a single layer of kimono) in yukata style (an informal cotton kimono's style) worn by Shinto priests, miko (shrine maiden) and ascetic Buddhist monks in divine rituals. It is also called Shiraginu/Byakue.
Originally, in the Heian period, Shiro Shozoku was worn under hakama (formal men's divided skirt), with cotton stuffed within, for cold weather. Later it got thinner and started to serve as underwear or underclothes for various kinds of costumes.
Presently, it is known as outerwear worn by miko over juban (undershirt for kimono).
Others
In the Heian period, white clothing used by people in the Imperial court as part of layered clothing, including silk costumes worn by emperors at the time of Shinto rituals, was generally called 'Shiro Shozoku.'
Basically ohenro san (pilgrim), who visits the Shikoku's eighty-eight sacred places, wears Shiro Shozoku, which is called Hakue.
Dead people are dressed in Shiro Shozoku, too. Shiro Shozoku for dead people is called shini-shozoku (a burial kimono) or kyokatabira (shroud). It consists of white hitoe, tenkan (golden crown) or triangle hood, tekko (covering for the back of the hand and wrist), kyahan (gaiters) and zudabukuro (a bag which is hung from the neck when a priest travels) which carries six one-mon coins for the world of the dead. It differs according to area and religious school.
As members of the Pana-Wave Laboratory were dressed in white from head to toe in 2003, media called them 'Shiro Shozoku Army' in order to emphasize their uniqueness.