Sei is a Japanese office lady in her twenties who was summoned to Salutania by the Saint Summoning Ritual together with Aira Misono. Her saintly powers include a fifty percent boost in the efficacy of anything she makes using her power. Sei was not immediately recognised as the Saint at the conclusion of the summoning ritual due to her appearance. Her daily dress is a red gown with patterns made out of gold swirls. She stopped wearing her glasses after the side effects of self-made facial cream.