Prologue

A certain Dungeon Core known by the number 629 was resting on a grassy plain as he managed his dungeon. He was a rabbit-type Dungeon Core with orange fur, and the first floor of his dungeon was in fact the grassy plain in question.

“Gosh. Where’re all the adventurers? This is super boooring,” Dungeon Core Number 629 said while bouncing around with three other rabbits. The other rabbits were technically dungeon monsters. Unlike normal rabbits, they had a single horn on their foreheads which marked them as Horned Rabbits, though that was about the only thing that separated them from normal rabbits.

“I got a grasshopper! Look, loook!” a rabbit said.

“Nom nom nom... Grass is tasty!” another said.

“Gaah! Who bit my eaaar?!” the third said. They were all having fun playing together. It was a very heartwarming sight.

Language-wise, Core 629 could understand them more than well enough thanks to being a rabbit-type Core himself. The only problem was that they weren’t too intelligent and didn’t always listen to his orders.

“Come on, you guys. Do your job and patrol the dungeon! Don’tcha want to eat carrots?”

“But I meaaan. You’re not motivated either, 629.”

“The weather’s niiice, the grass is niiice, why bother?”

“I wanna keep fluffing up my tail!”

Core 629 shook his head and sighed at the lackadaisical rabbits. His dungeon was peaceful, and while relaxing in the sun was fine, that wouldn’t earn him any DP. Killing grasshoppers only earned 1 DP. Locusts were 5 DP. In these grassy plains where humans rarely appeared, hunting grasshoppers was an important means of earning pocket change.

“Ah!”

A hawk suddenly flew across the sky. Carnivorous hawks were the mortal enemy of rabbits, regardless of whether they could talk or if they had horns. Hawks only saw them as food. Back when Core 629 had just started the dungeon and there was no underground floor, he had lost many good rabbit brothers to hawk attacks.

“Brothers, to arms! We must fight off the intruder!”

“Roger!” the three rabbits yelled. They would be dead if the hawk got them, and thus quickly went into their anti-hawk formation. Two of the Horned Rabbits formed a stand, onto which the third climbed. Then, Core 629 lifted up a paw.

“Okay! I’m peacing out! Good luck!”

“Whaaat?!”

“It only makes sense. This dungeon’s over if I die.”

“That’s true, but...”

“Isn’t this kinda cruel?”

“Oh, wait, the hawk’s coming. Fight, fiiight!”

The hawk ducked its head and shot down at high speed. The third rabbit waited for the perfect opportunity, then jumped, using the other two as a springboard for his attack. By jumping after the other two jumped, he could launch toward the hawk like a rocket in what could fairly be described as the ultimate horn tackle. Thus was their ultimate anti-hawk technique, the Bouncy Bouncy Attack!

“Oh, he missed.”

“Oof.”

“Welp, he’s dead.”

It was flawed, however, in that they only had one shot, and a miss meant a rabbit flying helplessly through the air. But still, despite the attack missing, the hawk halted its descent and flew back up for a second attempt.

“Don’t give up, brothers! We still have another chance!”

“But you’re about to run away, Core 629.”

“It’s fine! I’ll be the platform this time!”

They quickly got back in their formation, with Core 629 serving as part of the platform this time. A Horned Rabbit placed a foot on Core 629’s head and prepared for a second attack. The hawk lowered its head again and shot straight for the rabbits.

“Now! Bouncy Bouncy Attack round two!”

“Er, wait.”

“Ngh, what?!” Core 629’s legs buckled and he fell forward. The hawk shot down to seize the opportunity, but the rabbit they had launched earlier coincidentally fell and slammed into its head from above.

“Screee...?! Ngk!” The hawk fell to the ground, the poor landing killing it on impact.

“That was embarrassing, but I’m back.”

“Good job. I’ll groom your fur later as a reward.”

“We’re proud to be your older brothers.”

The three Horned Rabbits had a family hug. Core 629 took the opportunity to rub off the dirt stuck to his head and absorb the hawk corpse. That gave him 150 DP. Not bad.

“Hah. That hawk wasn’t a match for us after all. Easy win!”

“You tried to run away, Core 629.”

“Riiight? He totally did.”

“...What, you’re going to hold that over my head forever? Okay then! Take this! Reward strawberries!”

“Strawberries!” To rabbits, strawberries were a fantastic treat that they rarely got to eat. They would get stomach aches if they ate too many, but a small amount was the sweetest delicacy imaginable.

Buying a few with the DP he just got should be fine. Core 629 looked at the three Horned Rabbits and shook his head.

“Usually he only lets us eat grass at the Grass Spawner, yeah.”

“That grass tastes great, but strawberries are something else!”

“Eheheh, strawberries, gimme strawberries! This is why I bother patrolling at all...!”

“...Sheesh, here. Now get back to work. Unless you don’t want strawberries, I mean.”

“Strawberries!”

Incidentally, this dungeon—the [Rabbit Paradise]—had a pretty well-developed basement floor beneath the plains area. There were Wizard Rabbits that had mastered the arcane arts, Armored Rabbits that wore tough armor like an armadillo’s shell, and even Soldier Rabbits that could walk on two legs and use weaponry. They were deadly enough that newbie adventurers chasing rabbits underground were never seen again. Only one percent of adventurers survived the dungeon, being exclusively those who wisely turned back at the plains.

Thanks to its thorough efficiency in murdering intruders, the [Rabbit Paradise] remained a wild dungeon not identified by the guild, and although there were a few adventurers who knew there was a dungeon in the general vicinity, it was impossible to distinguish one unmarked plain from another. Many considered its existence just a rumor, or perhaps something they had seen in a dream.

＊ ＊ ＊

The [Rabbit Paradise] was as peaceful as ever. But that all changed when a certain intruder appeared.

“Well, what do we have here?! Is this a dungeon I spy?!”

The entrance to the dungeon was named the Rabbit Pitfall, and at the time everyone thought some more easy prey had fallen inside. They thought they could just surround the adventurer and beat him up as usual. However...

“W-Wait! Don’t attack!” Core 629 yelled, messaging everyone in the dungeon and halting their advance.

“What’s this, then? You beasts choose not to attack?”

Core 629 hopped out in front of the unfazed intruder, ignoring the several rabbits who told him it was dangerous. The intruder looked down at him and his fluffy orange fur as he emerged from the group of rabbits, then laughed derisively. But that was a worthy sacrifice. Core 629 knew for a fact that if his dungeon monsters attacked, they all would have died. He was sure of it. There was strength in numbers and in surrounding someone, but if the opponent in question was too strong, nothing would come from human wave tactics except a slaughter.

“Ermm, umm, are you a Dungeon Core? You’re in human form, but...”

“Oho! You are... not someone I remember. State your number.”

“I’m Core 629. What about you?”

“I am Core 564. An elite in the Demon King faction, of course.” The intruder—Core 564—gave a self-assured cackle. As a Core from the 500s batch, he was significantly older than Core 629, a Core obviously from the 600 batch, and on top of that he had the excess strength to transform into human form.

Not to mention that he was part of the Demon King faction. That was a gathering of Cores which excelled in individual strength, and Core 629 had heard more than a few tales of their conquests. Still, as a fellow Dungeon Core it shouldn’t be impossible to negotiate with this intruder, he thought. They all shared the same Father, after all.

The only exception to that would be the infamous traitor Core 89’s faction, but as a rabbit-type core, Core 629 belonged to the Beast King faction. Everything should be fine as long as he remained humble. Neither of them had been hurt or offended yet, and it was expected that younger Cores would show humility to older Cores.

“...My apologies, Dungeon Core Number 564. I would greatly appreciate it if you would leave my dungeon without causing undue damage. I can take you to the exit.”

“Hah! I’ve never heard a more boring proposition in my life. Why would a coward like you ever join arms with the traitor?”

“...Erm?” Core 629 tilted his fluffy head.

“Hmph. Why would anyone but a traitor make a dungeon in a place like this?”

“What do you mean by that? This is just a plain old field.”

“Playing dumb, are we...? Ah! Oh, I see, I see! This certainly is just a plain old field. Excluding the fact it’s located right in the middle of the warzone between the Empire and Demon Realm!” Core 564 roared with amused laughter.

Core 629, on the other hand, was blinking in surprise. He had never known that his dungeon was in such a hotspot of a location.

“Th-That’s news to me! I started this dungeon right where I was first placed!”

“I see, I see. And that’s why you joined the traitor faction!”

“Whaaat?!” The false accusations kept piling up, but to Core 564 it was the only thing that made sense. What were the chances that a neutral core belonging to neither faction would have a dungeon located right in the middle of a warzone? Slim chances, to be sure.

“It’s a coincidence!”

“There are no coincidences in war! You will not fool me!”

Core 629 was telling the truth, but the circumstances made it hard to believe him.

“I’m part of the Beast King faction! Can’t you tell that from my animal body?!”

“All I see is a weak rabbit. You must have fled to the traitor after the Beast King cut you off.”

It was so unfair he wanted to cry.

“Hmph. You are the exact kind of trash I would expect to see with the traitor. Now, I challenge you to a Dungeon Battle. I am willing to believe your words if you can beat me.”

“Whaaat?! N-No way could I beat you!”

“Then you recognize that you are part of the Traitor faction!”

“NOOO!”

“Heh, then our duel is inevitable. The date shall be... Hm, the gathering is coming up soon, so it can happen after that. You will have half a month to prepare after the gathering! Get what help you can from your traitor brethren, hah!” Core 564 cackled as demonic wings sprouted from his back and goat horns curled out of his head. “The Dungeon Battle will begin when I return! Wait warmly for my arrival! Bwahaha!” He flapped his wings and flew out the hole he had fallen through.

.........

For a minute, Core 629 stared in a daze at the hole Core 564 had just flown up through.

“Core 629, what do we do?”

“Ngh, I dunno... Ah! We need to ask the Beast King for help.”

“But how?”

On second thought, he had no means of communicating with him. Before now, he hadn’t even known the location of any other dungeons, which meant of course he didn’t know where the rest of the Beast King faction was. Sending a letter through a rabbit wouldn’t end well either way.

“...M-Maybe I can make Core 564 understand at the meeting?”

“That means we won’t have to fight, right?”

The Demon King faction was filled with battle-crazed blood junkies. It was difficult to imagine any of them giving up on a fight they had already resolved to have.

“Oh, right! I can just go ask the Beast King for help during the battle!”

“Will he make it in time?”

If Core 564 was to be believed, their dungeon was in an extremely inconvenient place. Any help he called would have to travel across either the Empire or the Demon Realm. That was over a month of travel, physically speaking. They would never make it in time.

“...Gaaah.” He was stuck. So stuck he had to cradle his head in frustration. But that was when he suddenly had an idea, one that might just get him out of this situation.

“...A-At this point, I’ll just have to ask Core 89 for help.” The idea sounded even better after he said it. Contacting her shouldn’t be so hard if he just went over to the Empire. They were both Dungeon Cores, after all. Should be easy. Yeah. If his dungeon was right between the Empire and the Demon Realm, her territory should be extremely close by.

Core 629 briefly thought of Core 695—Rokuko—who was undoubtedly part of the Traitor faction. She, at least, was more agreeable than those bloodthirsty nuts in the Demon King faction. It was probably likely that she would help. If he offered up his allegiance to them, in any case.

And so, Dungeon Core 629 decided to ask the Traitor faction for help. When danger was close, it was better to ask a nearby stranger for help than a distant relative, as the saying went.

“Who’s gonna go?”

“I don’t wanna go.”

“Me neitheeer.”

“I know, I know. I’ve gotta be the one to go... She won’t talk to anyone that isn’t a Dungeon Core, I think.”

Dungeon Core 629 steeled his resolve. All that was left was taking action.

“Watch out, be saaafe.”

“We’ll pray for you.”

“Our lives are in your hands.”

Core 629 left the plains as his rabbit friends casually saw him off. He opened his map and checked where to go. The sky was high and the wind felt great. His mood, however, was as glum as could be.

“...I’m sure adventurers come here from the imperial capital. So if I go in the direction they came from... Alright! I’ll protect everyone, no matter what!” Core 629 said before hop-hop-hopping off in the direction of the imperial capital.