Seventeen-year-old Yusuke Urameshi is a reluctant delinquent more interested in fighting than studying, but his life is cut short when he pushes a child out of the path of a speeding truck. As his body lies in the street, Yusuke’s spirit meets Botan, a cheerful guide who informs him that his death was unexpected. Brought to the Spirit World, Yusuke meets the ruler Koenma, who offers him a second chance at life if he agrees to serve as a Spirit Detective, an investigator tasked with stopping supernatural threats from the Demon World that leak into the Human World through a massive sinkhole that has opened in Sarayashiki City.

After accepting the role and being revived, Yusuke learns that his first mission is to recover three stolen relics of great power: the Rapacious Orb, the Mirror of Darkness, and the Conjuring Blade. His hunt brings him into conflict with a series of dangerous demons. He first battles Goki, a brutish yokai using the orb to steal children’s souls. Next, he confronts Kurama, a calm and strategic demon who has been reincarnated as a human boy and uses the Mirror of Darkness in a desperate attempt to save his dying mother. Finally, Yusuke faces Hiei, a master swordsman who has used the Conjuring Blade to unlock a powerful third eye.

As Yusuke takes on these missions, he is joined by his loudmouthed but loyal rival, Kazuma Kuwabara, who can also sense spiritual energy. Yusuke also forges an uneasy truce with Kurama and Hiei after discovering their motivations are not purely evil. To prepare for greater threats, Yusuke and Kuwabara seek out Master Genkai, a legendary martial artist who trains them in the use of their spirit energy, teaching Yusuke the powerful Spirit Gun technique and giving him the Spirit Wave Orb.

The team soon learns that a sinister plot is being orchestrated by Sakyo, a wealthy and ruthless criminal. Sakyo has been kidnapping demons, including the ice apparition Yukina, to exploit their powers and finance his true goal: opening a permanent rift between the Demon World and the Human World. To protect his operation, Sakyo employs the Toguro brothers, a pair of overwhelmingly powerful demons. The younger brother, a stoic master fighter, was once Genkai’s partner and kills her to prove his strength. The older brother is a sadistic, body-morphing creature.

Sakyo lures Yusuke and his friends to his island fortress by kidnapping Keiko, Yusuke’s childhood friend, and holding her alongside Yukina. There, Yusuke, Kuwabara, Kurama, and Hiei must fight their way through Sakyo’s forces. In a series of brutal one-on-one battles, Hiei defeats the explosive demon Karasu, and Kurama conquers the masked warrior Bui. Meanwhile, Kuwabara rescues Keiko and Yukina, learning that the ice maiden is actually Hiei’s long-lost sister.

The climax centers on a final wager between Koenma and Sakyo: if Yusuke can defeat Younger Toguro, Sakyo will close the portal. As demons begin to pour through the rift, Koenma creates a barrier to hold them back. In a desperate final battle, Yusuke channels all of his spirit energy into one massive Spirit Gun, ultimately destroying Younger Toguro. With his bet lost, Sakyo closes the wormhole and takes his own life. Yusuke and his friends return to the Human World, a team forged in battle, while in a mid-credits scene, the severed head of Elder Toguro washes ashore on a beach, still struggling to regenerate.