Masako was directly involved in the Hiki Clan Incident of 1203 alongside her father Tokimasa. The slain Wakasa no Tsubone was the concubine of Masako's own son Yoriie and the mother of her grandson Ichiman. The incident was the culmination of Masako's agonizing decision — as a mother — to depose her son and acquiesce in the killing of her own grandson. The vengeful spirit enshrined at Jakushi-do is the symbolic karmic echo of that choice.

Yoshitoki personally led the Hojo forces that attacked the Hiki residence in this very valley, where Wakasa no Tsubone took her life. The vengeful spirit enshrined here is directly a consequence of his violence. Later legend that his son Masamura's daughter was possessed by the serpent-spirit can be read as karmic retribution on the Hojo main line.

Father of Wakasa no Tsubone. Assassinated in 1203 by the scheme of Hojo Tokimasa, leading to the destruction of the entire Hiki clan at their Hiki-ga-yatsu residence. His daughter Wakasa, along with his grandson Ichiman, perished in the incident — she is said to have drowned in the family well. The legend of her vengeful serpent-spirit is a narrative born from the tragic fall of her father and the annihilation of the clan.