Sei was the spirit of a cherry blossom living near the cursed Ito-Jo. Due to the evil influence of the castle, her kin were decimated and her cousin was captured by the evil inhabitants of castle. In 1360 DR, she met an adventuring party hired by Michimori Uemon to recover the Seven Swords from the castle. She told them all about the damnation of the Ito family and warned them about the seven guardians of the swords.
Sei was shy and demure at first. She greatly resented all the death and misfortune brought by the Seven Swords clan and would help anyone who could stop this evil.