The Monster That Lurks Underground

 is an event taking place during the Tōjū Campaign. It focuses upon 11th Division 3rd Seat Ikkaku Madarame, Hōzukimaru, 4th Division 7th Seat Hanatarō Yamada, and 8th Division Lieutenant Nanao Ise's fight against the Tentacle Tōjū in the underground waterway beneath the Seireitei.

Prelude
At the Sōgō Kyūgo Tsumesho, 4th Division Lieutenant Isane Kotetsu enters 8th Division Lieutenant Nanao Ise's office and greets her before asking Nanao if she would like some tea. Wondering if she has been here for so long, Nanao apologizes for taking over Isane's desk like this.

Stating she does not mind, Isane says these temporary quarters make her feel like she has gone off to camp before stating she is somewhat enjoying it even though she knows it is silly. As Nanao smiles and says she knows what Isane means, Isane realizes something and reveals 5th Division Lieutenant Momo Hinamori brought in some cookies which she baked herself.

As Isane sets the cookies down on a nearby shelf, Nanao asks her if they look like the normal kind which one would eat. Confirming this, Isane asks her if something is wrong, prompting Nanao to deny this before stating she had a silly flashback as she recalls the glasses-shaped cookies which Momo baked for her before. Saying they look like normal cookies to her, Isane holds out the box of cookies for Nanao to see. Sighing, Nanao states this is a relief as Isane says she will get her tea. Walking over to the shelf, Isane expresses confusion and states this is weird.

When Nanao asks her if something is wrong, Isane turns around and says she cannot seem to find any of the tea leaves. Admitting this is weird, Nanao stands up and states she bought some the other day. Revealing many things have been reported missing lately, Isane says rice and soy bean paste were the first items to go missing as Nanao reveals 8th Division Captain Shunsui Kyōraku's secret stash of sake went missing the other day. Opening the door, 4th Division 7th Seat Hanatarō Yamada pants heavily before revealing Hanamaru has gone missing.

Later, as they look at a blurry photo of a figure taking a chicken, Nanao states this is all they have got before saying this is the clearest image which was caught by the surveillance cameras. Stating this is not much help, Shunsui says it could be anything. Stating they were unable to obtain any clear images, Isane reveals the intruder snuck into the barracks and stole four chickens. When 13th Division Captain Jūshirō Ukitake wonders why they have chickens, Isane says the 4th Division member have been too busy to go home between shifts ever since the Muramasa incident.

Stating the 4th Division members have tried to become more self-sufficient because of this, Isane reveals they now raise chickens and have started growing a vegetable garden on the grounds of their barracks. As Shunsui says their tomatoes and eggs are delicious, Hanatarō states it is a group effort and reveals he was in charge of raising the chickens. Saying they were all perfectly fine as of yesterday, Hanatarō begins to sob. Revealing the fence around the coop was perfectly secure and did not have any holes dug underneath it, Nanao states the culprit cannot be a simple-minded predator if it stole the chickens by opening the entrance door.

Noting the timing of this incident is very unusual, Isane wonders if it could be connected with the series of recent thefts at the barracks. As Shunsui sighs and wonders if this could be the work of one of the Tōjū, Ukitake asks 4th Division Captain Retsu Unohana what her thoughts are. Looking up, Unohana says they cannot eliminate the possibility before stating they do not have enough information to make any kind of conclusion. Revealing she traced the footsteps found at the scene, Nanao confirms the culprit escaped by accessing the underground waterway.

Later, Shunsui and Ukitake stand before Nanao, Hanatarō, 11th Division 3rd Seat Ikkaku Madarame, and Hōzukimaru as Ukitake reveals they were assembled here because they need to identify the thief who escaped through the underground waterway, track him down, and take him into custody. When Ikkaku asks him how this affects him and why he was summoned here, Shunsui says this is an easy question to answer before revealing the thief may be a Tōjū. As Shunsui states they want Ikkaku to protect everyone in order to be safe, Hōzukimaru says it will be a good way to pass the time.

Entering the Waterway
As Ikkaku agrees, Shunsui turns to Nanao and apologizes for involving her before stating he is counting on her to get the job done. Saying she understands completely, Nanao proclaims they are ready to go. Walking past the cheering 4th Division members, the group enters the underground waterway. Later, at the Shinigami Research and Development Institute, 12th Division 3rd Seat Akon and Rin Tsubokura observe the group on a monitor. As Isane, Shunsui, Unohana, and Ukitake walk up, Shunsui asks Akon if he is having any trouble tracking the group. Denying this, Akon tells Shunsui to see for himself.

When Shunsui asks him if this is the group's present position in real-time, Akon confirms this before stating that conducting a search while mapping the underground waterway is a lot for the group to handle. When Akon wonders if they are being too ambitious here, Unohana says they should not waste the opportunity before stating it is killing two birds with one stone. Noting it is dangerous, Isane asks Shunsui if they will be okay. Telling Isane to not worry, Shunsui says he is sure they will be fine. Meanwhile, the group walks along the underground waterway.

When Hōzukimaru notes this place has a creepy feeling about it, Hanatarō confirms this and states he has been hearing scary stories about it ever since he was a little kid. When Hōzukimaru asks him what kind of stories he is talking about, Hanatarō says they are stories about people who have died down here, people who have gone missing, and people who have been trapped here while extending the waterway. When Hanatarō states one can hear their voices calling for help when conditions are right, Hōzukimaru laughs and says this is a good one.

When Hōzukimaru states their thief may be one of the people who have been stuck down here, Nanao says this is ridiculous before stating these ghost stories are told to scare little children. As Nanao says everyone knows there is no such thing as ghosts in Soul Society, a drop of water falls on the back of her neck. Screaming in terror, Nanao states something touched her neck as Hōzukimaru asks her what is wrong. When Nanao continues to express terror, Ikkaku wonders if it was an enemy. Telling Nanao it is okay, Hanatarō walks up and tells her to not worry before revealing it was a drop of water.

As Nanao expresses surprise, Hanatarō points his flashlight upward and tells Nanao to look at the ceiling. Looking up, Nanao sees a tiled floor above her as Hanatarō reveals water seeps through the rock in several places. Noting Nanao was scared by a water droplet, Hanatarō says he never noticed Nanao was so easily frightened as another drop of water falls on Nanao's forehead. Laughing, Hanatarō walks forward, only to run into a tripwire. As Hanatarō expresses surprise, an explosion occurs where the group was standing as Ikkaku and Hōzukimaru, who is carrying Hanatarō and Nanao, appear several meters away.

As Hanatarō wonders what just happened, Nanao states he set off a booby-trap and says someone tried to wipe them out. Confirming this, Ikkaku states someone does not want them down here and says they are unwelcome guests. Adjusting her glasses, Nanao states this means the enemy is nearby and watching them before saying they will have to proceed with caution from this point on. Later, as the group continues to walk along the underground waterway, Ikkaku stops in surprise as Hanatarō bumps into him. When Hanatarō asks him why he stopped, Ikkaku points at something.

Telling the group to look, Ikkaku points at a discolored part of the floor in front of them and states it is definitely a trap. Noting it may be a hole or landmine, Ikkaku says putting it in the middle of the floor is a very amateurish move. Thinking, Hanatarō realizes something and walks forward while stating they simply have to walk along the edge of the discolored area. As Ikkaku tells him to not do it, Hanatarō steps on a hidden panel. As the rest of the group expresses terror, Hanatarō expresses surprise when nothing happens and laughs nervously before noting nothing happened.

As Hanatarō says he thought he was going to be blown to pieces, Ikkaku grabs him by the collar and angrily states Hanatarō almost killed all of them with his reckless behavior. As a tearful Hanatarō apologizes, Ikkaku notes nothing happened this time before saying Hanatarō was just lucky. When Nanao tells them to be quiet, Ikkaku sets Hanatarō down as Hōzukimaru asks Nanao what is happening. When Nanao turns to them and asks them if they hear it, Hanatarō asks her what she is talking about, prompting Nanao to state it is the sound of water.

The Tōjū Appears
When Hōzukimaru asks her if she is referring to the little drips from before, Nanao adjusts her glasses and says it is bigger before stating it seems more like rushing water. As Nanao says she hopes it is not headed this way, a large amount of water surges forward as the group expresses terror. As Ikkaku, Nanao, and Hōzukimaru, who is holding Hanatarō under his arm, run away as the water surges after them, Ikkaku states this answers Nanao's question before telling everyone to run for it. Noting it was a time-delayed trap, Nanao says the thief tricked them into thinking nothing happened.

Thanking Nanao for explaining, Hōzukimaru sarcastically states he will feel a lot better about things if he drowns as the water engulfs the group. As water bursts out of a hole in a wall, Ikkaku, Nanao, Hanatarō, and Hōzukimaru scream as they hurtle out of the hole. As they float in the water, Hōzukimaru asks the others if they are alright. As Hanatarō asks Hōzukimaru to define alright, Ikkaku wonders what this place is. Admitting he does not know, Hanatarō notes they were swept along for a considerable distance and says they could be anywhere.

When Ikkaku states Hanatarō is supposed to know his way around the underground waterway, Hanatarō says he knows his way around some of it and states he has never had a chance to come this far before saying this part is new to him. As Hōzukimaru notes it does not appear they will accomplish their mission, Nanao states they will all be lucky if they get out of here alive. As tentacles coil toward the group from under the water, Ikkaku says it is Hanatarō's fault because he failed at being their guide before expressing surprise when he is dragged under the water.

As Hōzukimaru calls out to Ikkaku, Hanatarō wonders what is going on as the bubbles where Ikkaku was dragged down stop coming up. Laughing nervously, Hanatarō tells Ikkaku this is a good joke before noting it is not very appropriate. As Hanatarō asks Nanao if she agrees with him, a large shadow appears underneath them as several tentacles burst out of the water. As Hanatarō, Hōzukimaru, and Nanao are washed away by the water, one of the tentacles holds up Ikkaku. Swimming toward the tentacles, Hōzukimaru tells Ikkaku to hold on and proclaims he is coming to save him.

As Hōzukimaru states he will be there in a minute, Ikkaku tells him to stay away and says he will try to figure something out. As Ikkaku tells the group to get out of here in the meantime, the tentacles drag him underwater once more. As Hōzukimaru, Hanatarō, and Nanao call out to him, a large wave washes them away. Later, the group sits on another walkway as Nanao wonders what they were just attacked by. Stating he cannot believe it, Hanatarō says this cannot be and states Ikkaku sacrificed himself to save them, prompting Hōzukimaru to tell him to not worry.

The Hooded Figure
As Hanatarō looks up in surprise, Hōzukimaru says a Zanpakutō spirit and its master have separate bodies before stating they share one heart. When Hōzukimaru says Ikkaku is not dead, Hanatarō thanks him as steam drifts past his face. Sniffing the air, Hanatarō asks Hōzukimaru and Nanao if they smell something. As Nanao expresses confusion, Hōzukimaru confirms this and wonders where it is coming from. Standing up, Hanatarō walks along the walkway until he comes across an alcove filled with items, a tent, and a campfire. As Hanatarō wonders who has been camping here, Nanao and Hōzukimaru approach.

Seeing five kebabs roasting over the fire, Hanatarō rushes over and states it cannot be before wondering if someone made kebabs with his chickens. As Hanatarō wails in sorrow, Nanao walks over to a table with several bottle of sake sitting on top of it and says she recognizes one of the sake bottles. Revealing this bottle was stolen from Shunsui, Nanao points out how it has Shunsui's name on it. When Hōzukimaru asks her if all of these items are the items which the thief stole from the barracks, Nanao confirms this as a cloaked figure appears before them.

When the cloaked figure expresses surprise and runs off, Hōzukimaru tells it to come back. Running along the walkway, the cloaked figure stops in surprise upon seeing Hōzukimaru standing before it. As Hōzukimaru states it is not getting away, the cloaked figure turns around and begins running the other way as Nanao and Hōzukimaru call out to Hanatarō. As Hanatarō looks over his shoulder, Hōzukimaru and Nanao chase the cloaked figure as Hōzukimaru asks him to help them head it off. As they run toward him, a panicking Hanatarō wonders what he is supposed to do.

Tripping, the cloaked figure falls out of its cloak and crashes into Hanatarō. Later, the figure bows before Hanatarō, Nanao, and Hōzukimaru and apologizes. As Nanao wonders why he is apologizing now, Hōzukimaru tells him to lift up his head and show them his face so they can see what he looks like. As the figure looks up at them, Hanatarō seemingly recognizes him. When Nanao asks him if he knows the figure, Hanatarō denies this and asks Nanao if she does. Sighing, Nanao tells Hanatarō to stop misleading them with inappropriate reactions, prompting Hanatarō to apologize for misleading her.

As Hanatarō admits there is something very familiar about the figure, Hōzukimaru leans toward the figure and demands to know what he did with Ikkaku. As the figure begins to apologize, Nanao leans toward him and demands to know who the figure is and why he is here. When the figure begins to apologize once more, Hōzukimaru angrily tells him to cut it out and asks the figure if he can say anything other than sorry. When the figure says he is very sorry, Nanao states this is enough and proclaims things are going to get ugly for the figure if he does not admit to what he did.

The Culprit is Revealed
As the figure sweats in fear, Ikkaku smashes through a nearby wall before crashing into the ground. Turning over several times, Ikkaku hits another wall and lies before the figure and Hanatarō, who calls out to him. As Hōzukimaru wonders what just happened, the tentacles appear in the hole in the wall as the Tentacle Tōjū roars. As Hōzukimaru says it is about time the Tentacle Tōjū showed himself, Hanatarō tells the figure he is responsible for this, prompting the figure to spin its head around while apologizing. Telling Nanao to protect the other, Hōzukimaru states he will take care of the Tentacle Tōjū.

As Nanao confirms this and runs off, Hōzukimaru holds his hands out and tells Ikkaku to not worry because the Tentacle Tōjū is about to be sashimi. As Hōzukimaru manifests in his hands, Hōzukimaru activates his Bankai, Ryūmon Hōzukimaru, causing a whirlwind to form around him. As the Tentacle Tōjū expresses surprise, the whirlwind dissipates to reveal Hōzukimaru spinning Ryūmon Hōzukimaru over his head while glowing with red Reiatsu. When Hōzukimaru throws the spade at the Tentacle Tōjū, it slips off of the Tentacle Tōjū's body.

Wondering if he missed, Hōzukimaru pulls the spade back, only to be constricted by two tentacles and lifted into the air as the Tentacle Tōjū roars. As Hōzukimaru tells the Tentacle Tōjū to let go of him, Nanao fires '''Hadō #31. Shakkahō''' at the Tentacle Tōjū's face. Blocking the blast with the fins on its head, the Tentacle Tōjū roars before throwing Hōzukimaru several meters away. As Hōzukimaru crashes into the water, Hanatarō notes the Tentacle Tōjū threw him like a ragdoll. When Nanao tells him he must he fight as well, Hanatarō expresses surprise as Nanao asks him what is wrong.

When Nanao tells him to stand up and attack the Tentacle Tōjū with his Zanpakutō, Hanatarō says his Zanpakutō is mainly used for healing. When Nanao asks him what he is saying, Hanatarō reveals he left his Zanpakutō at the barracks because he did not believe they would need it for this search. As Nanao states Hanatarō must be joking, a tentacle wraps around her and lifts a screaming Nanao into the air as Hanatarō calls out to her. As Hanatarō wonders how he will fight without a weapon, the figure looks at Hanatarō's Zanpakutō, which is lying on the ground nearby.

Drawing the sword, the figure stabs Ikkaku in the back with it. As Ikkaku expresses pain, Hanatarō tells the figure to stop doing this and says he will cripple Ikkaku. As the gauges on the sword and on the figure's face begin to fill, Ikkaku expresses happiness and states he feels great. Expressing surprise, Hanatarō says he knows this Zanpakutō spirit as the gauge on the sword fills up completely. As the figure's chest opens, a large cannon extends out of it and rests on the ground. As the figure releases Akeiro Hisagomaru, a red energy beam fires from the cannon and destroys the Tentacle Tōjū.

Aftermath
Falling into the water, Nanao floats on top of it and pants. Later, at the Sōgō Kyūgo Tsumesho, Ikkaku, Nanao, and Hanatarō, who has four chickens sitting on various parts of his body, stand before Ukitake and Shunsui, who asks them if they are sure the thief was the manifested spirit of Hanatarō's Zanpakutō, Hisagomaru. When Hanatarō confirms this, Nanao demands to know why Hanatarō did not tell them this before if he knew this. When Hanatarō apologizes and states he did not recognize Hisagomaru at first because he looked so different, Shunsui says this is not an unusual story for Hanatarō.

Sighing, Nanao reveals Hisagomaru was manifested by Muramasa and states he had no complaints about his master. Saying Hisagomaru tried to return to sword form as soon as he realizes what happened, Nanao states he was unable to do so despite his best efforts. Saying Hisagomaru eventually became depressed because he thought Hanatarō had rejected him, Nanao reveals he went to live like a hermit in the underground waterway before stating this is where they found him and told him what was really going on. In the past, Hisagomaru tries and fails to return to sword form in Hanatarō's room.

In the underground waterway, when a surprised Hisagomaru asks him if he is saying the reason Hisagomaru is unable to return to his sword form is not his master hating him, Hōzukimaru confirms this before stating none of the manifested Zanpakutō spirits have been able to return to their original form. Saying he had been thinking it was something he had done, Hisagomaru falls on his back, prompting Hanatarō, Nanao, and Hōzukimaru to ask him if he is alright. Confirming this, a blushing Hisagomaru reveals his body went limp for a second because he felt so much relief.

In the present, Hanatarō chuckles as Shunsui asks him if he ever discovered the truth behind the grilled chicken kebabs. In the past, Hisagomaru expresses surprise and reveals the kebabs are not his before stating he could never kill something to eat it. When Nanao asks him where the chicken came from, Hisagomaru reveals they were prepared dishes from the camp kitchen and runs over to a crate. Opening the crate, Hisagomaru reveals Hanatarō's chickens are here as the chickens fly out of the crate. As the chickens fly over to him, Hanatarō greets them by name.

When Nanao asks him why he took the chickens in the first place, Hisagomaru says he decided to live alone after Hanatarō rejected him before stating he wanted company because he was lonely. Telling Hisagomaru it is alright, Hanatarō promises he is not alone and swears to always be Hisagomaru's partner as they leap toward each other. In the present, Shunsui tells Hanatarō to hold on and says something is not clear to him before asking them where Hisagomaru is. Revealing they were separated, Hanatarō states they took opposite paths by accident and could not find him again. In the underground passageway, Hisagomaru sits by a fire and wonders where everyone went.