Chapter 1

My name is "Egusuke Kazuhiko." I am a middle-aged man, turning 40 this year, living in Edogawa, Tokyo. Professionally, I call myself a business consultant. I quit my job 10 years ago after obtaining a certification as a small and medium-sized enterprise (SME) diagnostician. I also hold a social insurance labor consultant qualification, so I manage to get by with social insurance-related work for SMEs in Edogawa, Koto, and even Chiba Prefecture, as well as occasionally giving lectures for training sessions. I get jobs through connections like my childhood friend, who owns a pachinko chain, or referrals from the SME Diagnosticians Association. That said, my annual income barely reaches 6 million yen.

Since I have no intention of getting married, I bought a small, 30-year-old house in the Kashiikotsu area of Edogawa, which is known as a "landlocked island." I work for two days, take a day off, then work for another two days, and take another day off. I lead a relaxed life with three days off per week.

"What is this hole...?"

Indeed. Until today, the end of June, just after the start of the Reiwa era...

Kashiikotsu in Edogawa is a vast "railway void" between Rikujou Station on the Toei Shinjuku Line and Koiwa Station on the Sotobu Line. It takes at least 30 minutes to walk to either station from my house. A 40-square-meter used single-family home can be bought for less than 30 million yen. I planned to live modestly in this small house with a garden, my final abode.

I felt a slight tremor late last night. In the morning, I found a hole about 80 centimeters square at the edge of my garden. Shining a flashlight inside, I saw a stone staircase leading down. I tilted my head in confusion.

"Basement? I don't recall any such information when I bought the house."

I checked my watch; it was 9:55. Since today and tomorrow are my days off, I had no plans. I took a flashlight and a lighter and slowly descended the stairs. The direction suggested it extended under my neighbor's house. I wanted to avoid neighborhood disputes, so I thought I should enclose the hole with a fence or something. While thinking this, I cautiously descended the stairs. The lighter remained lit, indicating there was oxygen.

"Wow, it's pretty deep..."

I had descended about 30 meters. Eventually, the stairs ended, and my feet touched the ground. I exhaled in relief and looked back at the stairs I had descended. They were quite steep, and the thought of climbing back up was a bit daunting.

"Quite a spacious basement. If I tidy it up, it might be useful for something..."

I shone the flashlight around. The basement was about 15 meters square, with a ceiling over 3 meters high. The floor was made of stone, with no gaps between the stones. As I observed, I stopped the light on the front wall.

"A door, huh?"

There was a sturdy metal door, at least 2 meters high. It was painted black, which is why I hadn't noticed it immediately.

"Air-raid shelter? Or perhaps a military facility from the war?"

The metal handle had no visible welding marks, as if it had been carved out. I thought it was necessary to check inside before reporting to the authorities, so I gripped the handle. At that moment, a sudden voice echoed.

"First contact confirmed. According to the World Law, the 'Dungeon System' is being activated. All dungeons will be activated in one revolution..."

"What? Where is this voice coming from?"

A mechanical, inorganic voice echoed. Surprised by its volume, I instinctively covered my ears, but the volume didn't change. It was as if the voice was resonating inside my head.

"Character Card 'Seductive Kunoichi Akane,' increase in card holding limit, expansion of ability slots, and skill selection function are provided as first contact rewards. The innate ability 'Card Gacha' has been set."

"Huh? Kunoichi? Card?"

"Dungeon Roulette complete, coordinates fixed. Dungeon name 'Abyss,' difficulty A, drop reward A, enhancement factor A. I look forward to your steps towards a new transformation."

Suddenly, the strange voice cut off. In front of me, a glowing white card floated in the air.

"...What is this?"

The sudden appearance of the mysterious basement, the strange door, the headache-inducing voice, and the incomprehensible content made the floating object seem trivial. The card itself emitted light, so I didn't need the flashlight.

Before reaching out, I observed it. A person was depicted on it, like a color photograph. A woman with black hair, resembling a ninja, was posing with a kunai? in her hand. I thought it might be a card from some card game. I reached out and took the card. It had a matte feel but was as hard as metal. On the back, text was written in Japanese.

＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝

【Name】 Akane

【Title】 Seductive Kunoichi

【Rank】 F

【Rarity】 Legend Rare

【Skills】 Kunai Technique Lv1

Reconnaissance Lv1

Sexual Techniques Lv1

＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝

"As I read, the card's light grew brighter. Blinded by the intensity, I dropped the card and turned away. The light disappeared after a few seconds, leaving darkness.

"Oh, are you my master?"

"Ah!"

A voice echoed from the darkness. This time, it wasn't in my head but a real voice. I shone the flashlight, and a beautiful woman with black hair stood there.

"Such a thing is tasteless."

In an instant, the woman snatched the flashlight from me, turned it off, and plunged us into pitch-black darkness.

"Please be at ease... the safety zone of the first floor will activate shortly."

"Who are you...?"

I asked the woman in the darkness, tense. A faint floral scent filled the air. Perhaps a sachet. After a while, my eyes adjusted to the darkness, and I could make out her figure. Then I realized the floor, ceiling, and walls were glowing. Gradually, a bluish-white light illuminated the room. The woman elegantly bowed.

"Pleased to meet you, my master. I am the ninja 'Akane.'"

"Akane...-san. Ah, I'm Egusuke Kazuhiko. To be honest, I'm confused and don't understand what's happening."

As I spoke, I couldn't help but stare at the woman's figure. She wore a fine chain mail top and a black outfit over it. Her lower body was clad in a dress with slits on both sides for ease of movement, revealing her shapely, yet slender legs. Most striking were her breasts. The chain mail seemed to hug her, and her well-formed, large breasts stood out prominently.

"Hehe... I feel a lecherous gaze."

"S-Sorry."

I turned away, but the alluring scent from the woman tickled my nose.

"Don't worry... I am your servant. This body is entirely yours. I know techniques to please men, and if you wish, I can do anything..."

"No, that's not..."

As I turned away, she blew into my ear, and I jumped back. Akane smiled coyly.

"Hehe. Are you calmer now?"

Only then did I realize I had been manipulated. I exhaled deeply. Indeed, I was calmer. To recover from confusion, it's best to look away from the situation. Calm, I began to organize the information I had.

"The sudden appearance of the underground space, the unknown voice and incomprehensible content, the glowing card and the woman in front of me... the information I need to grasp is..."

About 60 seconds later, I stopped.

"I want to ask you... no, Akane-san. What is the 'Dungeon System'?"

The woman moistened her lips with her tongue.

"My name is 'Akane.' I am one of the 108 pillars integrated into the Dungeon System. When I first saw you, to be honest, I was disappointed. You are middle-aged and overweight, and you don't look strong at all. As a man, you don't seem attractive. Yet, you leered at my breasts from the start. If you had tried to assault me, I would have cut off your head. The 108 pillars have the right to choose their masters.

"S-Sorry."

You turned away. At least, you're not someone who acts solely on male desire. You seem confused, so let me help you calm down. I could comfort you with my hands, but that doesn't seem necessary.

"Wait for one minute."

As you commanded, I silently observed you. You seemed calm, with a glint of intelligence in your eyes. You must be organizing information in your head. You seem to have a rational mind that suppresses instinct and a wise judgment. You lack a bit of vigor, but you're not a bad master. If you show the courage and determination to face this chaos, I might be willing to dedicate myself. Oh, it seems you've finished thinking. What is your first question?

"The Dungeon System is one of the laws governing this universe, the 'World Law.' I don't know the reason for its existence or its purpose. Just as water flows from high to low, the Dungeon System is a natural law.

"Over the next year, 666 dungeons will gradually appear in this world. Each appearance will be simultaneous, with 66 to 67 dungeons appearing at once, repeated 10 times. Most will appear in places where people gather, as dungeons are attracted to the number of people."

"I see. You mentioned 'one revolution.' So, my next question is, can you explain my understanding and correct me if I'm wrong? First, the dungeons I imagine are like giant caves underground, filled with countless ferocious beasts that attack people. Is that right?"

"That's correct. To be precise, they are not underground but in a different dimension."

"I see. I'll ask about the different dimension later. Tell me more about the dungeons. For example, if you defeat the beasts that appear, do you get something in return? I want to know the 'features and rules' of the dungeons."

"Understood. I will explain the dungeons."

"First, about the difficulty of the dungeons. The lowest difficulty is D, and the highest is S. There are only seven S-level dungeons. The next difficulty, A, is about 10%, or 60 to 70. Most are B and C, making up about 70% of all dungeons. The last 20% are D. The difficulty is determined by the number of floors in the dungeon and the strength of the monsters that appear, but it's not uniform. For example, there are B-level dungeons that are close to A and others that are closer to C. The difficulty also significantly affects the rewards you can obtain from the dungeon."

"I want to know more about these rewards. Are they like magic stones or materials?"

"Yes, that's possible, but in a civilized society, 'money' is often the reward."

"Huh?"

Money? Do you get a million yen or something when you defeat a monster? No, it hasn't been issued yet, so it would be a 10,000-yen note? I imagined it for a moment.

"Dungeons provide rewards that are valuable to the world they appear in. In some worlds, it might be food, in others, water or even air. But in more advanced civilizations, 'money' is often the reward. Of course, it's not always the case..."

Money appears when you defeat monsters. So, civilians will enter dungeons to get rich... I never imagined such a light novel scenario. If money appears in dungeons, the government will definitely regulate it. Currency issuance is an economic policy. The amount of currency issued annually affects employment, prices, and exchange rates. A dungeon that creates money at will would never be allowed by the government.

"Money appears, so people will try to enter dungeons... If you think the Dungeon System is flawed, you're wrong. The government would never allow such a thing. It would definitely be regulated, and the police or the Self-Defense Forces would suppress it. I don't know if automatic rifles work on monsters..."

"The Dungeon System operates dungeons autonomously. It might provide rewards other than money. However, the method of destroying dungeons with military forces won't work because weapons cannot be brought into dungeons."

"Huh? What do you mean? Weapons can't be brought in?"

"Yes, this is the core of the dungeon. Let me explain about 'cards.'"

Akane took a kunai from her waist and showed it to me. Suddenly, it turned into a card, like a magic trick.

"This isn't a magic trick. It's part of the Dungeon System. Weapons cannot be brought into dungeons. When the dungeon identifies something as a weapon, it is converted into a card. To revert the card back to a weapon, you must return to the 'safe zone' at the entrance of the first floor."

"Weapons can't be brought in? Then how do you fight in the dungeon?"

"There are two methods. You can fight using weapons obtained in the dungeon or have a servant like me fight for you. If you choose to fight yourself, it's best to search the dungeon for weapons while fighting monsters bare-handed. Only 'dungeon-produced' weapons can be brought into the dungeon."

"I see. What about the second method, 'servants'?"

"When you defeat a dungeon monster, it may drop a card. This is a servant. Servants can only be summoned in the dungeon and can fight on your behalf. You can also obtain servant cards from traders, who are interdimensional merchants who travel through dungeons, or by freeing sealed spirits."

"I see. So, you can be a warrior or a summoner. But why are you here? I haven't fought anything yet?"

"You are the first person to touch the Dungeon System. As a first contact reward, you received several benefits. Say 'status.'"

"Huh? Status..."

A black screen about 50 cm tall and 30 cm wide appeared in front of me, with white text floating on it.

＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝

【Name】 Egusuke Kazuhiko

【Title】 First Contact

【Rank】 F

【Card Limit】 0/∞

【Skills】 Card Gacha

------

------

------

------

------

＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝＝

"Hehe... As expected of the first contact. Your card limit is infinite, and you have six skill slots."

"Huh? Can you see it? And the card limit is the maximum number of cards you can hold, right? Six skill slots are surprising..."

"First, this status screen only appears in the dungeon, but others can see it too, so be careful. The card limit is the number of cards you can hold in the dungeon. Normally, it's 20 to 30, but because of the reward, yours is infinite. As for the skill slots, they are usually 2 to 3. However, I'm not familiar with 'Card Gacha'..."

"Ah... That's fine. I can guess. But the card limit is 0. You're not included, are you?"

"I'm manifesting because I'm a Legend Rare. In the dungeon, you can obtain monster cards. What do you want to do? Do you want to enter the dungeon now?"

"No, I need to prepare. Let's go back to my house and talk more. Let's return for now."

As I said this and tried to go back up the stairs, Akane didn't move. She sighed and said apologetically.

"As I mentioned, servants can only be summoned in the dungeon. If I go outside, I'll turn back into a card. If you want to talk to me, you have to stay here."

"I see. Is there any penalty for manifesting you again?"

"No, not really..."

"Then, can you turn back into a card? I want to write down the situation and, well, I've had to go to the bathroom for a while."

"Yes. And one last thing, please call me 'Akane' from now on. Being called 'Akane-san' confuses me. I am a servant..."

"Akane... Got it. Then call me by my last name or first name, not 'master.' It confuses me."

"Understood. Kazuhiko-sama..."

I was about to say, "Not 'sama'..." when Akane turned back into a card with a pop. This time, it didn't float but fell to the floor. I quickly picked it up and carefully put it in my chest pocket.

I realized something was off when I came out of the bathroom and was taking a break under the exhaust fan. Checking my smartphone, it was just past 10:00. I checked my watch, and it felt like at least 20 minutes had passed with the exploration and talking to Akane. However, the watch I had worn in the dungeon showed 10:30.

"What's going on? Is my watch broken? Or..."

I thought of a possibility and instinctively covered my mouth with my left hand.

"Is the flow of time different?"

I immediately set up an experiment. I prepared two quartz watches, wore one on my wrist, and tied a string to the other. I synchronized them and started the experiment. First, I lowered one watch down the stairs. The second hand started moving rapidly. I quickly pulled it up, reset the time, and lowered it deeper this time. After exactly one minute, I pulled it up. The watch, which had started at 0:00, was nearly two hours off. From this experiment, I was certain. Time moved faster in the dungeon than outside.

"Just to be sure, I need to ask Akane."

Bracing myself for muscle pain, I started descending the stairs again.

The comic version of "Dungeon Busters Volume 4" will be released soon