According to the "Engishiki" (codes and procedures on national rites and prayers), mo has two types which are hitoe mo and awase (lined garment) mo depending on the season, and the code stipulates the wearing of the two types of mo, the outer mo and inner mo, however, it became single (hitoe) mo only due to the collapse of the Ritsuryo system (a system of centralized government based on the ritsuryo code) and the prosperity of native Japanese culture.
『延喜式』によると、季節によって単衣の裳と袷の裳があり、また表裳と下裳と2種類の裳を着用するよう定められたが、律令制の崩壊と国風文化の興隆により単の裳だけになっていったと見られる。