Many decades ago, the god of Amawakuni was in anger and caused an ice age to occur throughout the country. Not long after, the Emperor of Hinowa (Shou of Tsukuyo) calmed the god, recreated life and reborn a new way of life. He then create all Hayagami. These Hayagami can now chose their own Shou.
Shou can use different abilities and powers from their Hayagami called Kamui (神意, Kamui). With these Hayagami, Shou can face war or chaos that can protect them. Being a Shou changes their fighting style,talent skill,way of living or ability of how to used to do before. However becoming a Shou is not easy as people anticipate. There are enormous effects to it Shou's physical and mental conflict will arise them.
When people became a Shou,time freezes for them meaning they stop aging aside their mental state. Eventually Shou can actually choose to stop or continue to age depend on their situation with the exception for the Twelve Shinshou.
They can have a lot of freedom as they want and do whatever they want,but it never last long when battling other Shou. Having a battle with other Shou is called a submission contest. Shou will battle other Shou in order to win their Hayagami. Either they want them submit to power up their Hayagami or submit to be able to wield the Hayagami that were already submit within them. When a Shou loses the contest,their Hayagami loses the will to fight back and has no choice but to submit to the Shou who won. Submiting to other Shou will absorb their Hayagami and their soul to the Hayagami and will be trap and lost within it forever.