Seishi Bosatsu is a bodhisattva from Buddhist tradition, embodying boundless wisdom. In Pure Land Buddhism, he serves as a primary attendant to Amida Nyorai alongside Kannon Bosatsu, with Seishi representing wisdom and Kannon compassion. This attendant role is consistent in all depictions.

Within the anime narrative, Seishi possesses a bright and friendly personality. He demonstrates deep care for the other buddhas, fulfilling a protective and supportive role within their group. His portrayal includes contemporary elements like a dedicated hobby of muscle training. His noted dietary preferences include protein and onigiri prepared by his brother, Kannon Bosatsu.

Seishi and Kannon Bosatsu share a fraternal relationship, with Seishi identified as the younger brother. This brotherly bond underpins their collaboration in supporting Amida Nyorai and assisting the thirteen buddhas in confronting Māra, who seeks vengeance against Shaka Nyorai.

Seishi Bosatsu's fundamental role, abilities, and relationships show no significant evolution or alteration across the available media. His narrative function remains centered on providing steadfast support to the buddha assembly, utilizing his attribute of wisdom.