Mina Saiki is a central character in the supernatural story Sky High. She begins as a young woman engaged to be married to detective Kohei Kanzaki. On her wedding day, she is brutally murdered by a supernatural serial killer who steals the hearts of his victims. After her sudden death, Mina arrives at a liminal space known as the Gate of Hatred, where the entity Izuko, the Guardian of the Gate, greets her. There, she is presented with three options for her afterlife: to accept her death and ascend to paradise for reincarnation, to wander the living world as a ghost, or to curse the person responsible for her death and bring about their end, an act that would condemn her to eternal torment in hell. Mina is given twelve days to make her choice.

Initially confused and overwhelmed by the circumstances of her death, Mina’s personality is marked by a strong sense of attachment to her former life and a deep desire for justice. Her motivation shifts from simply understanding what happened to actively confronting the killer who took everything from her. As she pursues the serial killer, who is attempting to resurrect a darker entity, she grows more resolute and begins to understand the weight of the decision before her. Her journey is guided by the previous Izuko, who teaches her about the role of the gatekeeper.

Through this process, Mina transitions from a victim into a figure of authority in the afterlife. She ultimately becomes the new Izuko, taking on the mantle of the Guardian of the Gate. In this role, she gains the ability to guide other departed souls, presenting them with the same three choices she once faced. Her key relationships include her fiancé Kohei Kanzaki, who investigates her murder; the supernatural serial killer Tatsuya Kudo; and the former Izuko, who mentors her. Her development is defined by her movement from a personal quest for vengeance to a broader responsibility for the fates of others, a transformation that shapes her into the enigmatic keeper of the gate between life and death.