Three thieves steal the Reikai Treasures, killing many onis in the process.

In the Urameshis' new apartment, Atsuko wakes up her son in tears. She's still devastated because of his recent death and resurrection, and is afraid he might fall asleep and never wake up.

Two boys walk towards Sarayashiki High School; one shows the other a dragon-carved pen that was made especially for him. The other comments that if Yusuke were alive, he sure would want to steal that pen.

Yusuke comes from behind and greets them with a hug. Thinking he's a ghost, the boys run away. Yusuke is uneasy about it, but Keiko comes from behind and reminds him that most people don't know he's alive yet.

Yusuke remembers the kiss and feels uncomfortable next to Keiko, but all she does is to chide him for getting late at school. Yusuke bitterly concludes nothing has changed between them.

At the school front yard, everyone is startled by Yusuke's return; no one comes to greet him. Keiko shrugs: "They never liked you very much before." Yusuke begins to regret having come back, until Kuwabara arrives with a contented smile and challenges Yusuke for a new fight: "I'm gonna send you back to hell!" Okubo nudges him: "Hey Kurama, aren't you going to thank him for having saved your cat?" Kuwabara shrugs him off, saying he will, but the fight comes first.

Yusuke smiles. Now he's sure nothing has changed at all.

Iwamoto-sensei watches Yusuke's return from a distance, and decides he's gonna find a way to expel the boy from school.

Yusuke skips gym class and goes to the roof. He finds a small lens in his pocket and remembers being given the magic object by Botan. She told him the lens is one of the seven objects a Reikai Tantei can use in his work. It allows him to see through walls, to find things that are hidden. He used it to look at Botan (probably through her kimono), and received an oar on his head for the impudence. Yusuke replied moodily that he wasn't interested in that Tantei job, and Botan snorted: "Okay, so I'll just tell Koenma-sama that he can take your soul away again." Clearly Yusuke has no choice in the matter.

Back to the present, Yusuke takes a nap on the roof. When he goes back to his classroom, his classmates are complaining that several objects have been stolen while they were in gym class - including the dragon-carved pen. They accuse Yusuke, the only one who wasn't at the gym class. Keiko tries to defend him; Iwamoto-sensei comes in and asks what the trouble is.

In the teachers' office, Iwamoto socks Yusuke, refusing to listen to the boy's claim of innocence. Takenaka-sensei is less sure of Yusuke's guilt and asks Iwamoto if he has any proof. Iwamoto: "I pondered about it and concluded he's guilty. During all the time he's been away there was no stealing case in the school. His mother begged so he could resume his studies here. (to Yusuke) I wonder if you inherited your mother's character..."

Yusuke is furious: "I don't give a damn about what you say about me, but I won't stand you talking about my mother!" he prepares to punch Iwamoto, who is actually looking forward it; it's the perfect opportunity to expel him from school.

However, Koenma arrives just in time, paralyzing Iwamoto and Takenaka so they can't see him. He's frantic, and tells Yusuke that the three demons that stole the Reikai Treasures have escaped to Ningenkai. Koenma's orders are to go after the thieves, but Yusuke argues that he has to solve his own problem first. Koenma tells him to use the magic lens to see inside Iwamoto's pocket. The dragon-carved pen and all the other objects are there.

Koenma "unparalyzes" the teachers, and Yusuke grabs the pen from Iwamoto's pocket, showing it to Takenaka. Iwamoto leaves the room, abashed and claiming it was Yusuke who put the objects in his pocket; Takenaka follows him, demanding an explanation.

Yusuke is still too angry to let go, so Koenma suggests that he take his revenge discreetly by using his new power, the Reigan: the energy of his aura being discharged in a powerful shot from his right index finger. With it he knocks Iwamoto down, without being noticed by either of the two teachers; but he's warned by Koenma that he can only shoot the Reigan once a day.

Koenma describes the Reikai Treasures: the Kouma Sword, which can turn humans into demons; the Mirror of Utter Darkness, which summons the energy of Evil in the full moon nights; and the Gaki Ball, which absorbs children's spirits. With these objects, the three thieves have the power to conquer Ningenkai.

Yusuke sighs: "I have no choice. Now that I resurrected I have to work for the humanity's sake, right?" He patrols the streets, looking for the thieves. He's about to give up when he finds a small crowd surrounding a little kid who has passed out. Having some eerie feelings about it, Yusuke jostles the crowd and sees the kid's spirit leaving the body.

He remembers what Koenma told him about the Gaki Ball, so he follows the spirit by the streets to a dead-end alley full of mean-looking guys. Yusuke wonders which of them is the demon thief, until he "sees" five horns in one guy's brow. Using the magic lens, he sees the Gaki Ball in the guy's pocket.

The other men pick a fight with Yusuke. He beats them up easily, but the demon thief took advantage of the distraction to disappear.

At Reikai, an oni informs Koenma of the identities of the thieves: "Kurama, no criminal antecedents, can change shapes, has supernatural agility; Hiei, no previous crime, unknown character, does not measure consequences to get to his goal; Gouki, twelve crimes registered, huge supernatural power, eats human spirits, killed several chasers."

Botan barges in Koenma's office by walking through the wall, complaining that these three are too dangerous for Yusuke. Koenma says that his intention was preparing Yusuke gradually, starting with small cases, but now there's no time for a smooth training; Yusuke has one week to retrieve the Treasures before Enma-daiou comes back from his trip. Koenma and Botan shiver at the idea of the dreadful things King Enma is likely to do in his anger, such as causing earthquakes in Ningenkai or even erupting the Mount Fuji. Botan decides to warn Yusuke about this deadline.

In Ningenkai, Yusuke gets to a park. It's raining. At a distance, he sees a supernatural blue light.

Hiei is swinging the Kouma Sword, cutting tree trunks that are briefly turned into demons. He and Gouki make plans of using the Treasures to take over the Human World, but Kurama tell them he's leaving the group. Hiei is furious: "Coward! While you hid here, you got yourself completely involved with the Human World!" Gouki demands that Kurama return the Mirror of Utter Darkness. Kurama: "I can't. I need this Mirror badly." Gouki is about to punch Kurama to get the Mirror when Yusuke arrives and introduces himself as a Reikai Tantei, demanding the return of the Treasures.

Kurama simply walks away: "I'm sorry, but I can't be captured yet." Hiei follows him: "Wait, Kurama, our talk is not over!" Yusuke is pissed with the two demons' "lack of manners", but Gouki stays to face him. He takes the kid's spirit from inside the Gaki Ball and eats it.

Yusuke kicks his stomach, and Gouki coughs the spirit out. The spirit flies back to the kid and Yusuke thinks the problem is solved, but Gouki is on his feet again and turns into his true aspect: a muscular five-horned sharp-fanged brown-skinned demon.

Yusuke is in shock. Their fight starts and Gouki is clearer the stronger of the two, specially since Yusuke has already used his Reigan today.