AN: Before I start the story, I'll answer a few questions: Yes, this is an AU. The timeline butterflied as soon as Iyahiro was born. Just like in real life, history doesn't repeat, but it does tend to rhyme a hell of a lot so that's why it's so close to canon. Other side effects were Irina's family leaving 2 years later than canon and Odin dicking around trying to escape his wife. (This is me trying to justify my lack of research, I'm reading the manga and light novel as I go)

Here I am, in bed, and HOLY FUCK am I sore. Mil-tan, you really don't fuck around, do you?

And once again, I feel metal on my wrist again, my sacred gear, Dominus Tempus. I think that bad latin for Master of Time or some shit like that.

Since the parents are currently visiting our aunt, breakfast naturally falls on me, since Issei can't cook for shit. I get my ass out of bed and stumble around into the kitchen.

[Wake up! Wake up!]

Issei slept through his alarm again, and I'm the one suffering for it. I hear the damn thing all the way in the kitchen, how are you not awake yet, Issei!?

I grab a few eggs and Oh Fuck!

…

And now everything is now in super slow motion…

Ooooh! so that's how you use a sacred gear, like using a muscle you never used before…

…

Well that was easy!

I grab the eggs out of the air and stop using my sacred gear. Time resumes…

…

Holy shit I'm practically DIO now!

Anyway, I grab the rest of the ingredients and start cooking.

"How did you do that nii-san?" Issei's shocked voice comes from the hallway.

"Learned it in a dream." Technically true, though the ape was barely of any help.

Rias, in uniform and all, comes out of Issei's room.

"Oh, hi buchou, didn't expect to see you here." I comment, now fully awake, "eggs will be done in a few minutes," I decided this was a good chance to test out speeding up time, I put a small amount of energy in my sacred gear. Eggs are done over easy in 2 seconds, "or now."

Rias' face was of slight shock but soon turned into a pondering face. I could practically see the gears turning behind her eyes. So she was thinking for once, good for her.

I scoop the eggs onto her plate and speedrun cooking the rest of the food with the help of my sacred gear. At first the feeling of using it was unnatural but soon enough, it just felt like using another arm or leg.

Once I was done, I looked back to my plate.

"Itadakimasu," The three of us said at the same time.

Hot damn was the food good. Good job me! The eggs were cooked cleanly, over easy just the way I like it, the hash and sausage looked like something Gordon Ramsay would make, and the bacon was cooked to crispy perfection.

Issei and Rias had a look of bliss upon their faces, stroking my ego like a high-end hooker.

With this day starting out at such a high point, Issei and I got ourselves ready and walked straight back to the hell that is high school.

~ORC clubroom, after school~

Turns out that I needed that pick-me-up since our classmates were being extra annoying today. Especially with the dumbest rumors possible coming out of their sewers. Thankfully, they were mostly about me and not Issei this time. Seems like someone had the good sense to end their peeping habit; only took like a literal fucking decade.

This time, the rumors were about me being in the Yakuza. Apparently, someone saw me training with Mil-tan on the range and made the connection that I was some sort of enforcer. This also had the side effect of morons trying to challenge me, not fucking fun.

So now, buchou's agenda for tonight is to train our sacred gears for an hour and do contracts for the rest of the time. The track and field were slotted for us so we walk the way there.

When we arrive, everyone gets set: Jailbait starts punching the air, Akeno sits on the ground reading a tome of some kind, and Mr. Perfect starts shitting out swords Emiya style. That leaves Issei and I under the personal attention of Rias Gremory herself.

fwoomph

Issei summons his badass gauntlet and Rias approaches him. This time, while Issei is distracted by staring at her tits, she studies the gauntlet in detail, looking for something.

"Now Issei, do you feel anything inside you, like something waiting to burst out?"

Issei breaks his stare off of her and looks off in the distance, scrunching his eyes in contemplation.

"...Actually, wait I do feel somethi-"

{BOOST}

The gauntlet flashes for a half second.

"WHOA! I feel so much stronger!" Issei exclaims excitedly. He starts punching the air and running around a bit, getting a feel for it.

As quickly as it came, the power soon goes away, with Issei satisfied with his discovery. Rias' eyes widen suddenly as she made some sort of connection.

"… Twice Critical." She mumbles out.

"That's the name?" Issei replies.

"Oh! yes, that one boosts all of your abilities twice over-" Rias starts explaining.

"YAHOO-"

"-but only once."

"...oh." That put a damper on Issei's mood.

A minute later, she turns her attention towards me and approaches.

"Now earlier, I saw you using your sacred gear while making breakfast. Mind showing me it again?" She takes a marble out of her pocket and hands it over to me.

I drop the marble and, at the same time, activate Dominus Tempus. The marble very slowly falls through the air. I try increasing and decreasing the energy I feed into it and the marble responds by falling slower and faster. I let go and the marble falls to the ground.

I look for it and right next to it is… the same marble?

I reach out with my left hand and it flies up to my fingers.

…What?

I place that marble down on the ground and ponder what the hell is going on.

Wait… didn't the monkey-man say something about "inversion" or something? OH… OOOH! What a mindfuck!

Alright, so, if I feed energy into the thing allows me to slow or speed up time, what happens if I taking away energy.

I decide to try that theory by grabbing the original marble and activating the sacred gear. The other marble rolls over to the original, picking up speed. When I stop taking away energy from the marble through the gear, the marbles merge and the result is just one marble on the ground. I pick up and pocket the marble.

Alright, what the fuck happened here?

I looked towards Rias but she was no help here since I saw complete befuddlement in her eyes. Now, like the good scientist that I am, when I'm confused about something on an inanimate object, I immediately move onto live subjects. So I ponder on how to "take energy" from myself.

In my pondering, something appears right on front of my eyes, myself. He walks backwards a few steps.

"?kcuf eht tahW" He says in weird reverse speech.

The other me then turns around and at this moment I figure out how to take energy from myself through the gear. I start walking forwards, he starts walking backwards and in the exact instant I stop taking energy, we merge.

I walk a few more paces before I realized something's off. Everything sounds like a video played in reverse.

I turn around.

Wait…

"What the fuck?" I stare at my own confused reflection.

I walk forwards to see my self closer and in an instant, I'm back where I was before everything was inverted.

I turn around once more to see Rias have an existential crisis, and the others, including Issei, stare slack-jawed at me.

Well this is awkward.

~One hour later~

After an hour of trying to process the weirdest 5 minutes of my life, I think I figured it out. Sp essentially, if I push my willpower/energy "forwards" through my sacred gear, I can manipulate forward flowing time. If I pull it "backwards" out of my sacred gear, I could temporarily reverse the flow of time for myself or an object. Theoretically, I could manipulate the speed in this reversed state as well but I haven't tested that out yet.

Still though, what the fuck…

I look around, everyone is still looking at me like I just summoned Cthulhu.

…

blip

The sound came from Issei.

"Oh… wait my first contract," Issei says in shock, finally shaking off the mindfuckery involving me.

…

"Wait, how do you teleport?"

"The flier is supposed to do that for you." I answer. Wait… Is his demonic energy that weak?

…

"Looks like you're gonna have to bike all the way there then." I quip.

"What?..." Confusion… then panic spreads across his face. He runs like a bat out of hell out of the building.

I'm sure he'll be fine.

He was in fact, not fine.

AN: Nice little filler for y'all and the movie that I ripped off was Tenet, that is all. See You Next Chapter!