Why is my Isekai in the Slice of Life anime was become a Horror Story?

Mission 1: The House of Whispering Corpses

Chapter 1: I'm Sure I've isekai into a Slice of Life Anime World

I have isekai.

This method of isekai is impressively primitive in its beauty.

On my way home after buying instant noodles, sausages, and eggs to treat myself to a grand meal,

Takahashi Takakai heard the shrill sound of a car horn blaring behind him. When he turned around, he saw a truck, out of control, charging toward him as if to scream, "Surprised? It's time to reincarnate into another world, Shounen!"

And just like that, he was struck, soaring into the sky, falling to the ground unable to move, and then once again crushed by the truck's wheels. His head was flattened right on the spot, and so, he dead.

The feeling was probably like a watermelon being hit by a baseball bat, smashed to pieces, and splattered everywhere.

However, Takakai wasn't entirely sure he had really died such a miserable death. After all, in the last moment before losing consciousness, he had indeed seen the truck's wheel up close, heard the screams of bystanders, and the sound of phone cameras snapping photos.

Before dying, he just hoped no one would find his 69GB "homework" folder. As for his web browser, he had used incognito mode, so it should be fine... probably.

Ahem, let's stop here. No need to discuss such adult topics.

Anyway, after dead and isekai'd, he found himself in what seemed to be the place of someone else in a normal Japanese family. The name on the health insurance card he found at home was "Takahashi Takakai."

By the way, Takakai was certain he had isekai'd with his body, not just his soul, because his height, build, mole, and other detailed features hadn't changed at all.

Even the clothes he was wearing were the same old ones, still bearing traces of tire marks and a sticky red-and-white mixture, just like before.

Speaking of which, the dried red-and-white stain... could it be my brain?

After travelling, Takakai was given a two-story house with its own garden. Inside, there was also a bank card with a balance of eight figures, and the password was written on a small note attached to the card. The card's owner was also Takakai.

After rummaging through the house's documents, Takakai speculated that he might have travelled into some parallel world.

Because the person named Takahashi Takakai, who existed in this world, the person he replaced, was almost exactly like him, only slightly thinner. This person, like his previous self, had long since lost his parents and become a member of an orphanage.

During his investigation, Takakai discovered that the original Takakai in this world had a habit of writing a journal. Although most of it was just random scribbles, it still painted the picture of a young man who had dropped out of school and lived off a huge savings, enjoying a comfortable life.

He spent all day holed up in his house playing games, watching anime, completely isolated from the outside world. This made Takakai relieved that he wouldn't have to deal with relatives or friends after travelling.

"Really, who writes a journal anyway?"

After carefully investigating the house and grasping the situation, Takakai held the journal left behind by his "other self," unable to help but marvel.

Anyway, it seemed that there was no way back.

Even though he had replaced the life of this person, if there was no other way, since he had come here, he would live for this person from now on.

Moreover, upon further consideration, the circumstances after traveling seemed pretty good. No parents, no family, no friends, plenty of money, a house already set up—it was as if everything had been perfectly arranged.

Could it be that I'm really the protagonist in some novel, carrying some sort of mission on my shoulders and about to accomplish something great?

Takakai, a Webnovel author who lived alone in a small rented room in his previous life, couldn't help but start daydreaming.

"Well then, typically, the protagonist after isekai would have some sort of cheat ability. Let's see, if I'm the orphaned protagonist, it's probably a System."

"Of course, the sign-in type is the best. After all, this type of System is usually quite relaxed, suitable for... being lazy."

"So, do I have a System? System, are you here? System? System-chan? System-sama? System-sensei? Hmm, seems like there's none."

After a while of trying to call the System, he didn't get any response. It was just him standing in the middle of the room, looking like a fool, trying various postures and tones to summon it.

"Alright then, looks like there's no System. At least the start of the story seems like a regular life without a System. That's fine, fighting and killing isn't interesting anyway; a peaceful life is the true path."

Eventually, feeling a little foolish for just standing there calling out, Takahashi Takakai stopped, coughed lightly, and then climbed to the second floor, heading into the specially designed gaming room of this world's Takakai.

He weaved through various gaming consoles placed around a corner of the room, made his way to the computer by the window, pressed the power button, and then began to search for news and basic information about this world, aiming to clarify the environment he was now living in.

By the way, although the search results were all in Japanese, Takakai could easily read and understand everything, even speaking it naturally. Moreover, when searching in other languages like English, French, or Arabic, he also understood the meanings and could pronounce them perfectly.

"So my cheat ability is knowing every language in the world?"

This ability didn't seem all that useful though...

But for now, there was no need to worry about this. After all, upon thorough investigation, Takakai confirmed that this world wasn't that different from his previous one. Overall, it was still a peaceful and normal world, without anything supernatural.

There were no reports of cannibalistic monsters operating in the shadows, no Fuyuki City with gas pipes exploding continuously, no Umbrella Corporation, no Miskatonic University, the sun wasn't rapidly aging, and nothing was flying in from outside the solar system. Yep, it looked like this was an entirely normal world.

Hmm, although it's also possible this world has a dark side operating in secret, in general, it still seemed like a place where ordinary people could live their whole lives in peace.

Thinking this way, Takakai continued searching for information in Japan, and then he came across "Shuchiin Academy."

"Shuchiin? Isn't this the setting of Kaguya-sama: Love is War? The famous romcom that later became a dubbed the 'giant of love'?"

"Got it, I've travelled into an anime world!"

Takakai had to admit he was a little excited.

He kept searching and quickly found information about the Shinomiya Group. This almost confirmed that this was the world under the pen of Akasaka Aka. Though the plot later became a bit heavy, just stepping into an anime world made Takahashi excited.

"No, I can't conclude this just yet, I need to investigate further."

"First... Ah, Suimei Art University? If there's a middle school affiliated with it, doesn't that mean Sakura-sou also exists?"

"And also, Guitar Hero is trending on the internet right now, so Bocchi is here too."

"Next, let me check if there's a Toyogasaki Academy or Sobu High... Hmm, no. Looks like Yukinoshita and Kasumigaoka aren't in this world. Anyway, they are heroines who have appeared in many fanfics, so there's probably them in it somewhere."

(TN: lol, when I read fanfics SoL, I've never seen a fic without both of them at the same time, maybe 9/10 fanfics)

"In other words, I've travelled into a crossover anime world? And it seems like it's a slice-of-life anime world too?"

Takakai turned off the computer, sat down in a chair, and began to sink into thought, sorting through the clues.

First off, he was an orphan who had been transported to a different world, replacing someone who looked exactly like him.

He had the ability to understand all languages, owned a large house, and had a hefty amount of money, ensuring he didn't have to worry about basic living expenses.

This Takakai seemed to have almost no social relationships, which meant any obstacles to adapting to this world were minimal.

Then, there were cute anime girls in this world, which made it very likely this was some kind of crossover anime slice-of-life world.

So, doesn't that mean I'll become the protagonist of a harem fanfiction?

Although he was a bit disappointed that there weren't any older or younger sisters, like in the usual harem genre, the next developments would surely be fanservice-heavy, with all kinds of benefits coming his way, right?

"Wow, thinking about it, this new life might actually be pretty exciting~"

While Takakai wanted to pretend to be noble, he had to admit that he was someone who actually enjoyed darker things. He couldn't help but think of a few things that, if written down, would surely get censored and removed immediately.

At this moment, he started imagining whether he'd become the protagonist of a harem SOL anime and go through exciting scenarios, even thinking about whether there would be a group of unemployed fat otaku readers following his journey, eagerly awaiting scenes of him conquering each beautiful girl.

Ahem, that's a story for later. What's more important now is investigating the house thoroughly to prepare for any situation.

At the basic level, he had gathered quite a bit of information about the family's situation. He had already searched through most of the house, getting a rough understanding of the furniture layout and architecture. However, there was still a small shed in the yard that looked like a storage room, which he hadn't checked yet. Maybe he would take a look at it later.

After confirming the situation with the house, he planned to use the computer to research the street layout around the area, then go outside to explore the neighborhood and get to know the surroundings.

In general, Takakai wanted to get as much information as possible under his control.

For him, this had become an instinctive reaction. Even in his previous life, whenever he made a decision, he would always find ways to thoroughly investigate the place. Whether it was watching a movie or anime, he would look up the cast, seiyuu, directors, scriptwriters... Even though most of the information he collected wasn't really useful, he still found it incredibly interesting.

Swish, swish, swish—

He opened the sliding door leading to the yard and put on the shoes that were right in front of the door.

Dreaming about his future life, Takakai stepped into the yard and walked towards the small, seemingly ordinary shed at the corner of the yard. He tried to pull on the door. When he realized it wasn't locked, he opened it.

Immediately, a gust of cold air rushed out from inside, making Takakai shiver.

"Why is it so cold in here? The weather's still pretty warm outside..."

Feeling a bit strange, Takakai took out his phone, turned on the flashlight, and shone it into the shed. He discovered that it was just an ordinary storage room, filled with brooms, shovels, a lawnmower, and several fabric bags containing seeds, all emitting a dusty smell.

The cold breeze from earlier seemed to have been just an illusion.

"Seeds, huh? Are they planning to plant something in the yard? Should I follow the tradition?"

Takakai mumbled to himself as he stepped into the shed. His gaze immediately stopped at a small black box sitting in the farthest corner of the shelf. There was a note stuck to the box.

"Placed here so specially, could this be some sort of secret prop?"

Since isekai, Takakai had been investigating for a few hours without finding anything strange, so he thought for a moment and decided to reach out and take the box down to check it out.

The box seemed to be made of metal, and it felt cold to the touch.

It had clearly been placed in a dusty shed, yet the box showed no dust whatsoever, and even reflected light slightly, as if it had just been manufactured.

Takakai bent down and looked at the note on the box. It only had one sentence written on it:

"Don't let anyone know where you're from."

"What does this mean?"

Before Takakai could think much more about the meaning of the words, the lid of the box let out a small "click" and automatically opened.

At that moment, Takakai's vision was consumed by complete darkness. In the blink of an eye, he lost consciousness.

In the midst of his drowsiness, Takakai heard a voice.

A voice that could not be distinguished by gender, impossible to tell what it belonged to, but just hearing it was enough to send chills down his spine, as if someone were quietly laughing right beside him.

It said:

"Welcome to the 'Sacrifice Game.'"

"Your game level: Dusk."

"May you witness the end of everything, amidst true terror."