Izuko is a beautiful and mysterious woman who serves as the Guardian of the Gate to the afterlife. Her solemn responsibility is to guide the spirits of the recently deceased as they arrive at a crossroads, presenting each soul with three distinct choices for their journey forward. A soul may choose to accept its death as is and pass through to Heaven to await reincarnation. It may instead refuse to accept its fate and remain on Earth, wandering as a ghost. The third option is to seek justice for the wrongs suffered during life, taking revenge into its own hands, but with the dire consequence of then facing the gates of Hell. Most souls arriving before Izuko are victims of murder or other untimely deaths, and each episode typically follows a new guest character who must come to terms with the circumstances of their demise. Despite Izukos compassion and her earnest attempts to guide them toward peace, her efforts do not always lead to a happy resolution, and the moral dilemmas the spirits face are often complex and deeply unfair.

The television series is set in contemporary Japan and unfolds across nineteen episodes, initially airing from 2003 to 2004. It is a live-action adaptation of the manga Skyhigh by Tsutomu Takahashi. The story is further enriched by a theatrical prequel film, released between the two seasons, which reveals the tragic origins of the enigmatic gatekeeper. In life, Izuko was a young woman named Mina, a bride-to-be who was brutally murdered by a supernatural serial killer. After her death, Mina found herself in the underworld where she was guided by the previous Izuko. When that guardian was slain in a sword duel by a demon, Mina inherited the guardians sword and the title of Izuko. She was then forced to confront and defeat her own demonic killer, an act that cemented her new role as the permanent Guardian of the Gate. The second season of the television series incorporates visual elements from this prequel, giving Izuko a darker, edgier costume compared to the softer look of the first season.

Throughout the series, Izuko encounters a wide array of spirits, each with a unique and often heartbreaking story. In one episode, she helps a young woman found murdered in a river investigate the shocking truth behind her own death. Another episode features a man who died a hero saving a woman from attackers, but who is haunted by the irony that he was only in that position because he had been spying on her. Izuko also counsels an exchange student who was a victim of bullying, attempting to convince her to reject the path of revenge. A three-part thriller in the first season follows a young woman named Anna who, with Izukos help, uncovers a shocking truth about her own murder and parentage through the pages of a cryptic novel. In the second season, Izuko assists a family torn apart by a fatal drunk-driving accident, helps an Olympic hopeful who died in a fire encourage a fellow injured athlete, and guides a criminal defense attorney who must solve her own murder from beyond the grave while wrestling with her desire for vengeance.