Seigen Kusanagi is the patriarch of the Kusanagi Clan, a lineage historically tied to exorcism. He is grandfather to Yuma Kusanagi and a veteran exorcist within the clan's hierarchy. Keenly aware of his granddaughter's latent potential and Matoi Sumeragi's developed exorcist abilities, he discreetly oversees their activities in the conflict against the higher-dimensional entities known as Nights. Seigen presents himself as a reasonable figure when dealing with other exorcists involved in this multi-dimensional conflict.