Kai (嵬) is the name by which those who participate in the Dance of Gasara are referred to within the Gōwa Family. It appears that not all members of the Gōwa clan are Kai. Monoyose is another name for a Kai, as well as Invitator (インヴィテーター), the name by which the mysterious organisation Symbol refers to those with abilities like that of a Kai.
Kugutsu is the original term for Kai and is used to describe clans of Kais ("Kugutsu clans"). Both terms refer to people who have specially harmonized body and minds which can summon the power, Gasaraki. They are able keep memories of their past life.