Here I present

Schrödinger's Sanity

A fanfic based on the concept of High school DXD, borrowing its world and all that.

Have fun reading this one chapter. I'm just putting this idea out here so I don't forget about it. I didn't even watch any of the anime, and got most of my plot knowledge from reading other fanfictions. Please point out my mistakes, if I have made any.

-Spirit

...

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Secondary Author Note (Written 12/10/2020)

I've looked at the fics in this fandom and basically all there is are gary stu fics, smut fics, and the rare well done combination of both. Oh, and betrayal fics. A lot of them. The rare gem is in there, but uh... I haven't found them.

It's not that they're bad (except the ones so filled with angst that they're unreadable). The first two that I read were fun up till chapter ten or something, but it just really gets old fast.

This is the idea of an anti gary-stu: a person with no plot significance and basically no real power trying to understand what happens from a normal perspective. (If this even makes sense.) I introduced the sacred gear just for comedic purposes.

Hope you enjoy this experiment.

(Slight Edit: Thanks to Wilted12 (I hope I spelled that right) to pointing out that one mistake about Gasper still being sealed away. I literally just looked at the wiki's affiliations page.)

…

Walking into Kuoh Academy, past the red walls that separated it from the streets, I, Tantei Keiji, knew something was wrong.

Our family, a long line of private investigators, trailing back to the age of dynasties, always had a sense of when things went wrong. Shivering, as I approached the school's gate, I felt an odd sense of foreboding

It felt really weird, like ice was slowly sliding down my spine. I had just passed something unseen.

. I adjusted my glasses and peered forward. It appeared nothing was there, but it certainly didn't feel like it.

"Son," I remembered my father saying, "That school… gives me the shivers. Since your sister is going there, we need to investigate. View it as your test to inherit the family business."

Whenever people in my family got the shivers, we always knew something was wrong. My grandfather uncovered a psychopath's hideout when he thought he heard "the screams of the damned" coming from a newly constructed sewer. My father had unearthed a crime syndicate while on an investigation completely on accident.

Either way, our family trusted our instincts. When we thought something was wrong, something definitely was up. My grandfather was also incredibly superstitious, and although I dismissed his insistence of having to pray for protection to the gods as crazy old man talk, I still felt uneasy when I left the house without the protective charm that was strung on my pencil case's keychain.

My sister, Sakura, stopped behind me.

"What's wrong?" She asked, putting a hand on my shoulder.

"We might need to get out the cork board and yarn later today." I said cryptically. "Otou-san said there was something off about this school and I'm feeling it too."

"Don't worry about it." My sister said, pushing me past the gates. A lot of people were already staring at me for staring at the boundary of the school like there was some sort of unseen force field preventing me from entering. "I've been here for a year now, and nothing bad has happened. What could go wrong?"

…

Rias Gremory looked out from the student council meeting room's window, which overlooked the courtyard.

One sacred gear wielder was entering the school this year, and a powerful one at that. The Longinus, also known as the Boosted Gear, allowed its wielder to double their power in various time increments depending on the familiarity with the gear. Issei Hyoudou, the current wielder, did not have it unlocked yet, and was blissfully unaware of his hidden power. The boy looked unremarkable, with brown, spiky hair and an average figure.

Well, there was the other sacred gear user. Tantei Keiji. User of the Spectacles of Warning. The sacred gear was unique in its own way, but quite useless in general. It was regarded as some sort of joke in the supernatural world.

The gear's powers were so useless that it merely provided a warning to the user about impeding danger. Ironically, the more dangerous the situation got, the more delayed the warning signal was. Its wielders had solved some crime cases with it, but only because the dangerous event that had occurred in their surroundings had occurred in the past. It contained so little energy from God that it couldn't even manifest into the world in the form of a physical object or a spirit.

Other than that, it also gave the wielder terrible eyesight (hence the name "Spectacles of Warning", because all of its wielders wore glasses), a slight boost in running away from situations, and a bit of awareness of the supernatural.

She doubted that even low level stray devils would consider attacking the holder of the gear, because they possessed so little magical energy that subduing them and absorbing their life force probably would result in a negative mana trade because the latent boost to the user's evasion techniques actually made them harder to catch.

The only unique aspect of the gear was that it replicated itself when the user procreated, and was the copy of the gear would be passed onto the youngest child.

Wait, did the wielder of the boosted gear just get slapped? She had to see this. It wasn't every day that anything interesting actually happened.

…

The classes in this school were totally normal. There were a couple of annoyances (Another boy in glasses that didn't bother to keep his hormones in check), but other than that, nothing out of the ordinary.

What was fishy about this place?

For now, I was content to lose myself in the introductions of the new student. There weren't a lot of other boys, so the only odd thing compared to a perfectly normal school was the gender ratio.

Now that I come to think of it, that was odd in itself. The gender ratio. A previous all-girls academy suddenly allowing boys to join?

It wasn't like the school lacked money or anything. In fact, the costs to refurbish changing rooms and all that for our eventual physical education classes would probably cost much more than the additional revenue of having more students would bring.

All in all, it was an impractical business move.

"Tantei-san, please introduce yourself to the class."

Oh, right. Self introductions. It was my turn now.

I walked up to the front of the class, noting the whispers of most of the students. The only other male in the room, the annoyance that was casting unsightly glances towards our fellow classmates. I didn't bother to remember his name.

"Greetings, my class. My name is Tantei Keiji. I enjoy mystery novels. Please take care of me throughout the year." I bowed stiffly, and walked back to my seat.

The next person went up, and I fell back into my thoughtful trance once more.

...

The academy really was beautiful. Its campus was large, the lush grass was green, the sports areas were magnificent, and the architecture and statues were simply exquisite.

Some people clearly were not here to admire those things.

It had been a couple of months now, and nothing out of the ordinary had happened. My corkboard only had the two initial queer occurrences, and nothing more. Nothing seemed suspicious, even if my subconscious whispered at me to get away from a couple of people. Did I really dislike them that much or were they a legitimate threat?

They were high school students. How bad could they be?

Somebody sat beside me. It was probably my sister, and I didn't even pay attention.

"Enjoying the outdoors?" She said, smirking.

"Not really. Just… thinking." I said, looking up into the clouds.

"You still think something's off about this school?"

"There's nothing that indicates anything's amiss. It's just that…"

"Everything seems weird?" She said, "Come on now, don't be like dad. Remember when he panicked over something that was supposedly an horrible accident waiting to happen and it was actually just our pineapple about to fall onto the pizza? I mean, pineapple pizza is terrible but it doesn't warrant such a response."

She laughed.

"He was literally frothing at the mouth."

I remembered that moment vividly.

"Pineapple pizza isn't that bad! It's just food!" I protested, sitting up and glaring at her.

"It's disgusting and you know it."

"Is not!"

"Is too!"

..

And so, the school was treated to the sight of an accomplished member of the kendo club slap fighting with a freshman boy that was not actually part of the perverted trio.

"Well, that's not something you see everyday."

"At least he got some game going on…"

"How am I ever going to achieve my dream if some random person gets ahead of me first?"

…(A month later)…

I slammed open the front door to our apartment and ran into the living room.

"Sakura! Get the cork board and yarn!" I shouted, running straight into the drawing room.

"Seriously? We just put it away three days ago! I thought you finally stopped your useless investigation!" She groaned, opening the door to her room with a creak.

"You would not believe what happened."

Barging into the storage room, I sifted through the bunch of used cork boards (relics of past investigations that I had attempted in middle school) leaned up against each other, and pulled out the one about Kuoh academy.

Sakura came into the room, looking exasperated but still willing to comply. She lifted up the cork board and went out of the room, me trailing behind her.

Interestingly enough, she had always been the more athletic of the two. Sakura loved annoying me about it as we were growing up until I stopped paying attention and began to discover what would be the prime focus of my elementary school and middle school career… reading mysteries.

"So, why are you bringing out the conspiracy theory wall again?" Sakura said, putting the cork board on the table and lifting it upright so it leaned against the wall.

This room, the place that the family had designated as the mystery room, was the place where my dad and my grandfather had solved many of the cases they were hired to investigate. It was honestly really cheesy. The light was intentionally dimmed and was also one of those old fashioned hanging lamps that would dim once in a while. The room's other three walls hosted my dad's three finest cases, its "logical" thought process "clearly" outlined by an array of pictures linked by a "bit" of red yarn.

"I was an idiot not to notice it before. It was obvious." I said, sitting down on the leather armchair. Sakura pulled up the nearby wooden chair and placed it down in front of me, sitting down.

"What?"

"What was suspicious. It's not that the school holds terrible secrets. It's the people that do." I said, slamming down my fist on the armrest.

"So what's your working theory?", Sakura said, getting a cup of tea that she procured from who knows where.

"What can separate people from suspicious and normal… from inconspicuous to eye-catching… from harmless to dangerous…" I intoned, getting up and pacing around the room. Sakura watched me with interest, giving her expression that probably meant 'I'll humor this theory as long as it's not too crazy'.

I stopped in front of her and took a deep breath, then bent down slightly, pointed a finger at her face, and shouted,

"Is hair and eye color!"

The contents of her tea cup found them on my face. I recoiled and wiped it off with the hem of my shirt, before looking at my audience.

The teacup was lucky to be intact. Sakura was laughing so hard, slapping her thigh. The teacup rested on the armrest of the wooden chair and looked like it was about to fall off. I quickly snatched it off of its precarious position, placed it on the table, and continued.

"It's a truth hidden in plain sight. Rias Gremory, Akeno Himejima, Koneko Toujou, and Yuuto Kiba are the only people with a hair color that is not either black or brown."

"Doesn't Akeno himejima have black hair?"

"It's blue! A very dark shade of blue, but still blue!" I said, turning and face palming.

"… What's the point of this spiel?"

"The point is, there's something fishy going on about all of this. Especially since Issei Hyoudou was asked out by a girl with red eyes!"

Sakura actually looked mildly surprised. "That pervert actually got asked out?"

"Yes! I mean, no! That's not the point!" I gesticulated wildly, waving my hands and shaking my head, stopping only when my glasses threatened to fall off my face.

"Why would a random girl with red eyes just go out and ask out a famous pervert?" I said, pacing once more. "It just doesn't make sense!".

"What does this have to do with the Gremory group?"

"There's a Gremory Group?"I almost shouted, turning my head so quickly I thought that I had severed a tendon somewhere.

"Yeah. They always sit around each other at lunch and go to the Occult Research Club."

"Fascinating." I muttered, preparing a sticky note and thumb tack. I doodled a rough picture of each of the individuals, pined them to the wall, and connected them with the red thread to a sticky that said "Occult Research club."

"So there's a clear relation between all of these oddballs, and now somebody similar to them that doesn't actually go to our school asks out Issei."

I sat down back in my armchair, taking deep breaths and calming down from my sudden discoveries.

"… Is that all you have for a theory? No accusations?" Sakura said, tilting her head and sounding very confused.

"Unfortunately." I said, calming down and sighing. "We'll have to wait for Issei and the girl to actually interact to draw any conclusions. Maybe something will change…"

"This is ridiculous." Sakura said, sighing. "This is even crazier than the time you thought that tax collectors were secretly soul sucking demons out to drain the will of humanity."

"I was five and didn't know how taxes worked!" I said indignantly.

"Fine. If you're actually onto something and odd things happen after their date, I'll eat a slice of pineapple pizza."

"Deal."

And so we waited. For that fated day to come.

…

IDK if this story is actually understandable or just really cringe, but here you go! Something I was thinking about for about a week.

If you enjoyed, leave a mark (favorite, follow, review, etc) so I can now if people actually want this continued or not.

Thanks for reading this little drabble.

-Spirit

Basic physical descriptions of OC's: Tantei Keiji: Black hair, wears glasses, brown eyes, looks like all of the wallflowers in various animes. Likes pineapple pizza.

-Tantei Sakura: Keiji's older sister. About two inches taller, much more athletic, and also has black hair and brown eyes. Absolutely hates pineapple pizza.

Minor Edit: Changed some things to include honorifics and more Japanese language stuff. It's the details that matter in writing, folks. The details.