Each kingdom has a ruler chosen by a kirin, the longer a ruler has goverened their kingdom the more wealthy and enriched it becomes. To benifit the people of the kingdoms, the rulers are given immortality.
When a ruler is killed or dies, their kingdom will suffer from natural disasters and attacks from youma, so it is desired that a new ruler is chosen again quickly.
If a ruler does something against the heavens, like opressing the people or becoming currupt, their kirin will gets sick and will die unless the ruler changes their ways if a rulers kirin dies, the ruler will lose their imortality and will die within a year.[link title]