A pu (歩) is a unit of length. It is equal to two steps, which will differ slightly depending on which individual's steps are used as the base for the unit length. It is approximately 135cm.
One hundred square pu is known as pu (夫), or a pu of land to distinguish it from the unit of length. The measurement is notable because each adult in a kingdom is given one pu (夫) upon reaching the age of majority. "Each family gets two hundred square pu for farming and fifty square pu for a house".
A sei (井) is equal to nine-hundred square pu (夫). Collectively, the nine pu (夫) forms a hamlet. In a kingdom, three hamlets forms a village.