Buyaku refers to labor allocation imposed on subjects by each ruler in Japanese history.
During Japan's medieval period, a taxation system was established with nengu (land tax) and kuji (public duties). Kuji that were imposed on people were called buyaku, distinguishable from other kuji (also called zokuji).
These duties included serving as a soldier, a jicho (manservant doing odd jobs in a nobleman's house), Kyonoborifu (serving in Kyoto) or Kamakurafu (serving in Kamakura); other duties included working in a local area as a sumiyakifu (charcoal burner), kusakarifu (mower) or working in a tsukuda (rice fields managed directly by a lord or officer of a shoen [manor]).
After the Muromachi period, shugo daimyo (Japanese provincial military governors who later became daimyo, Japanese feudal lords), Sengoku daimyo (Japanese territorial lord in the Sengoku period) or their subordinates would recruit for these duties, putting private soldiers, servicemen or laborers into service. What additionally began taking place during this period was daisenno (paying dues in cash), which was paid in return for buyaku that involved actual manual labor.
Early modern times
During the Edo period, buyaku became a variety of komononari (miscellaneous tax).
Lords in the shogunate system imposed ninsokuyaku (physical labor) for construction, cleanup and traffic on the people inhabiting a fief. After the Edo period, however, the trend turned increasingly towards daisenno.
In this case, it was called 'buyakusen.'
Additionally, villages and towns sometimes used the word 'buyaku' in reference to ninsokuyaku (cleanup, construction, guard and porter) that they imposed on residents in order to maintain their own communal functions.