Kagan appears in the eyes as a flower shape in place of their pupils. No one is born with Kagan as it only appears during puberty. Each generation of House Hibari has used Kagan in their work as shinobi and thus Kagan marks the heir to their family legacy. Those who exhibit the mark have the power to become master hypnotists. In order to control it's power, the affected individuals follow a training schedule, also to prevent accidental "puppeting". and if mastered can be used to trun enimes into allies and and also to get information out of important people.
Those who possess the Kagan have the ability to control people's minds with the power of the Mystic Eye. The simple fact of looking in the user's eye is an open door for a possession, if it's activated.