Yosei live in large feudal clans, led by a busho, whose family came to power through military might and skill. Each family is headed by a choro, who is the eldest male, and the choro of the most powerful family in the clan is the busho. The busho's family controls all of the land in the clan's territory, and the choro controls the family's share of that land, which they employ peasants to work. The 12 bushos answer to the busho of the most powerful clan, who is called the ko eda, who takes tribute from every clan.

A yosei peasant works land that their family controls. Their choro pays tribute to the busho, who pays tribute to the ko eda. Poor families must rely on powerful families for protection, but powerful families will have some warriors of their own, called gado. The gados are low-ranking warriors who usually younger children from poor families seeking to gain more prominence among the clans. The busho's clan has its own warriors, taken from the ranks of the powerful families, called tsuriburedo. The ko eda, however, recrutis their own warriors, the most elite in the nation. These are called nobara. The warrior class are privileged in the yosei clans.

Also privileged in the clans are the mystics, known as mado-shi. Any yosei found to have especially powerful mystical powers or talent for use of mana is taken by the ko eda's forces as soon as it is known and taken to the special training academy for mado-shi. These serve only the ko eda directly.

Children are raised by their extended families, usually by parents and grandparents. They recognize four genders; marriages are arranged and gender is not a consideration for then. However, marriage does not exclude other relationships for the powerful. The very poor often marry to get out of poverty and have no other relationships (often being treated as slaves or servants). Those who remain poor and marry other poor folk do marry for love, sometimes, away from their lords' attentions.

By age 11, yosei children have manifested their basic powers and begin training to work the land, be warriors, be servants, or be lords. Some take on specialized roles for the family, but most are farmers. At age 25, they are adults and can be married, have their own households, or leave their families to join another if another will take them.

Yosei bond with trees to gain special powers. Every different kind of tree gives different powers, and these are special to each clan. The ko eda's clan is bonded to the spirit oak.

Many ceremonies exist among the yosei. Special ceremonies are held every day. One to honor ancestors (upon waking), one of gratitude for the land (at noon), one to keep away evil (before bed). Every week there are extra ceremonies. On the third day, they perform a ceremony to honor their parents; on the sixth day, they perform a ceremony to honor the ko eda. Every full moon, there is a ceremony to honor the sources of mana (for double and triple full moons, these ceremonies become more complex). Every year, there are five ceremonies: one to honor the coming year (new year), one to honor the first yosei ko eda (start of summer), one for the harvest, one for the end of harvest (Samhain), and one for the longest night. These 11 ceremonies are very important and must be observed for fear of bad luck.