In the Spirit Realm, Koenma wonders what is going on. There is a terrible storm outside, and he thinks that this amount of rain is not normal. Jorge then bursts in and exclaims that there's an issue with the river Styx. Outside, as several other ogres are making storm preparations, a massive tidal wave suddenly appears.

It crashes down over them and washes them away. Some of the ogres make it back inside, and close the main doors. The tidal wave hits the building.

Eventually it breaks the door down, and water floods the place. Jorge asks Koenma what they should do, as the water floods the offices.

Jorge tells Koenma that it's dangerous here, and he should seek refuge. However Koenma tells him to go and summon Botan, whilst he will be waiting in the great vault. A little later on, Botan appears, and sees the water everywhere.

She also sees Koenma being washed away, and has to chase after him. She eventually manages to get him onto a very small piece of dry land.

He gives her a glowing object, and tells her that she must hurry and take it to Yusuke -there's no other way to save the spirit world. He then tells her she must go now, as he's going to be remaining here. Botan takes off on her oar.

As she looks back she sees Koenma being washed away again. She bursts though the building and takes a look at it, and sees that it has almost been completely submerged.

As she flies off, she gets hit by a bolt of lightning, and crashes down into the water. The water continues to rise.

Yu Yu Hakusho:
Chapter of Underworld's Carnage - Bonds of Fire

At Sarayashiki Junior High, Keiko wonders where Yusuke is. Yusuke is up on the roof, thinking about how hungry he is right now. He's about to get get his lunch, when he sees Botan staggering above him.

As she falls, he catches her, and asks what happened. Botan mumbles something about the Spirit Realm, but doesn't say what. She then says they must go to the Kasane Shrine, and find Hinageshi. Before Yusuke can ask her anything else, she passes out.

Keiko arrives on the roof, and sees Botan. Yusuke says he doesn't know what's going on, but he asks Keiko to take Botan to Genkai's temple. Later on, Yusuke and Kuwabara head to the Kasane Shrine. Kuwabara asks why they are going there, but Yusuke admits he doesn't know. There was no time for him to get any details.

The two then hear a scream, and Yusuke uses Kuwabara as a springboard to get over a wall. At the shrine, a young girl is being chased by several men.

As she asks them what they want, they transform into demons, and continue to chase after her. But then Yusuke shows up, and starts beating them down.

He uses his shotgun technique on one group, but another group resume chasing after the girl. One of them grabs her and starts choking her, but Kuwabara then slices through his arm.

He summons his spirit sword, and starts slicing through the other demons. As Yusuke finishes his group off, Kuwabara notices some kind of cross marking on the head of one of the defeated demons, which vanishes. The girl realizes Yusuke and Kuwabara must be Spirit Realm detectives, and she introduces herself as Hinageshi -a guide of the Spirit Realm.

Everyone heads to Genkai's place, where Botan is still unconscious. Genkai says something serious must have happened in the Spirit Realm. A door opens up, as Kurama arrives. He tells everyone that the Spirit Realm is gone.

He explains that, more accurately, the Spirit Realm is now submerged in water. Kuwabara wonders how this happened, and Kurama believes some immeasurably strong power must have gained control. Genkai wonders what kind of power could have done it, and Kurama says that he saw some phantoms there, who had cross patterns on their foreheads. They were looking for something.

Hinageshi says it must be the nether world. The phantoms Kurama saw were demons controlled by the nether world, as their symbol is that cross. Kuwabara asks what the nether world is, because as far as he knew, there was just the human world, spirit world and demon world. Hinageshi pulls a book out and explains that above the human world, lies the spirit world. The two are in balance with each other.

She then explains that, originally, the nether world was above and in balance with the demon world. But then, several thousand years ago, the nether world began a war with the spirit world, in order to gain possession of the human world. It's not known how the nether world was defeated, but...

...she says that King Enma was finally able to destroy the nether world, and banish its King, Yakumo, and his followers into the darkness of space. Yusuke wonders how the nether world was able to come back into existence. Genkai says if the nether world has returned, it could become a very dangerous situation -they won't be able to repel them alone. Outside, Hiei has been listening in. But he doesn't think the the nether world has anything to do with him.

Meanwhile, Kuwabara goes crazy when he finds out Yukina is here. He rushes off to find her, and sees that she is with Botan. She says whilst she's glad to see him, she's worried about Botan. Kuwabara vows that he'll get all of this resolved, and they'll all be happily smiling again.

As he takes her hand, she asks him if he's alright -his temperature is going up and up! Kuwabara tells her that's the power of love. Yukina thinks Kazuma is so hard to understand. As Keiko arrives, Hiei also appears, but stays back.

Kurama asks him why he doesn't just tell Yukina that he's her brother. Hiei says he doesn't want his advice. Kurama tells him he must have seen what happened to the spirit world, and that this is no ordinary event. Hiei claims he's not interested, and jumps away. Later on, Kuwabara asks what their next move should be. Hinageshi says that they must transfer power to the spirit world. To to that, there are several places in the human world called elemental sites, which naturally collect spirit energy.

She says that are five of these elemental sites, with them each representing the earth, wind, fire, water and spirit elements. If these sites are all unsealed, their amassed spiritual power will be sent to the spirit world. Kuwabara says if that happens, the spirit world will be restored, so he asks where these sites are. Hinageshi says she knows where they are located.

In the city, a man is walking though a building, but then stops. He raises his arm and tells his servants to come forth, as he releases a powerful blast of energy, which obliterates everything around him.

Three streaks of light appear in the sky, and land behind the man. The lights change into demons, and one of them tells Lord Yakumo that his demon Gods have now arrived. Yakumo says that their strategy has now entered the second stage, and wants them to make the power of the elemental sites theirs. The three demons move out.

The next morning, Hinageshi leads Yusuke, Kuwabara and Kurama towards one of the elemental sites. But then everything suddenly shakes, and they then notice a beam of light nearby. Hinageshi says it's the elemental site that represents earth, so she and the rest of the group run towards it.

They see the light, but Hinageshi says it's too late -the elemental site has been destroyed. What is streaming out of it is not spiritual power, but nether world power. These demons are able to convert the spiritual power to nether world power, and if they manage to convert the energy from the other elemental sites... Kuwabara asks what will happen, and she reveals that it will mean the spirit world will remain inaccessible.

Yusuke says they need to hurry, as they've got to protect the other sites. Kuwabara suggest they split up, so they head to different sites. As Yusuke and Hinageshi head off, Hinageshi says she can't even repay Botan the kindness she owes her. She says she always made mistakes, and caused a lot of problems for Botan. Yusuke tells her it's too early to give up now. Hinageshi says the next site is up some steps behind them.

They head up, but Yusuke senses something is wrong. A building nearby suddenly collapses, for seemingly no reason. But they then see the cause.

A bunch of demons appear on the wreckage, and then head off. The two see that they are nether world demons, and chase after them. They follow the demons into an underground parking lot. Hinageshi points out that at the end of the lot is where the elemental site of fire is.

Some demons are heading right towards it, but Yusuke quickly runs over and defeats them all. He tells Hinageshi it's over, and asks what they need to do now. But then the power to the building and cars suddenly goes out.

There are then several explosions, and Hinageshi suddenly finds herself floating. Yakumo walks over, and covers her body in some kind of energy.

But he says she is not the one. Yusuke runs over, and Yakumo throws Hinageshi into him. Yusuke catches her.

Yusuke goes to attack him, but before his punch can connect, Yakumo warps around him. Yusuke turns around, only to be kicked hard by Yakumo, and gets sent crashing into a car.

As Yusuke recovers, Yakumo sees he must not be a regular human -he must be a tool of the spirit world. He introduces himself to Yusuke, and says he is the King of the nether world. Yusuke takes aim at him, and fires a spirit gun blast.

The blast is stopped by Yakumo, who protects himself with a barrier. Yakumo calls Yusuke's spirit power nothing, and tells him to get lost. He raises his arm and hits Yusuke with a blast of nether world energy.

As Yusuke collapses, Hinageshi goes to check on him. She then sees Yakumo walking towards the fire elemental site, and wonders why he's here. Yakumo destroys the site, converting the spirit energy to nether world energy.

A beam of light smashes through the parking lot, and heads straight up into the sky. Yakumo then turns around and walks towards Yusuke and Hinageshi...

...but then disappears, leading Yusuke to punch the ground in frustration. Yakumo returns to the spirit world, and thinks about the power sphere -an object that was the source of the nether world's energy, taken by the spirit world long ago. Once it has been returned, their hopes will finally be realized. The leaders of the spirit world must have hidden it well, and he wonders where it could be.