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English
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Published:
2024-09-18
Updated:
2025-02-01
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21,702
Chapters:
4/?
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That one rule

Summary:

Nagi Seishiro is a recognized scientist who discovered how to travel through parallel universes. After visiting other dimensions, Nagi comes to the conclusion that he is the only version of himself who is not dating Mikage Reo.

Notes:

Based on this tiktok: https://vm.tiktok.com/ZMhL9Q5rv/

Also please don't pay too much attention to sci-fi related terms

Chapter 1: I know you

Chapter Text

Ah, I really want to go home.

Seishiro was advised to wear sunglasses and to keep his head down. Watch your steps, let the bodyguard guide you, don’t speak unless asked to. He follows the orders, maybe just lacking a certain professionalism and charm that comes from years of interacting with fans in this type of situations.

In this universe, cameras follow him and flash to capture his every step. Nagi walks down the red carpet dressed in a very expensive suit that feels a little too tight on his waist. He answers questions that he already knew were coming so his only task was to memorize the answers. The news outlets will report his attitude that night as cold and mysterious but very attractive anyway.

Seishiro, the scientist, finds himself inside the cinema’s auditorium and listens to the speech of a movie director who also lives in his dimension. The director mentions Seishiro’s work and asks for a polite round of applause because if it wasn’t for you, Nagi, this project would have never been complete.

Those were the same words that came from his boss the moment his experiment, the multi-dimensional traveling machine was complete. He wonders if every single one of his lives is up to some great accomplishments. He almost feels bad for stealing this moment from the Seishiro of this dimension, the actor.

When the movie starts, he can’t help but feel weirded out by seeing himself (but not really) playing the main role of an action movie. There are guns and explosions, and of course, a great mission to save the world. A girl that he doesn’t know but who is seated beside him is playing his romantic interest. For a moment, they focus on the expression of Seishiro, the actor, and Nagi, the scientist, can swear he sees plain disinterest in his eyes before he leans in for the kiss.

His night is over after a celebratory party that he leaves rather early. His manager, or something of the sort, drives him safely to his apartment. Once in front of the door, he realizes he doesn’t have a key, so he knocks on it a couple of times.

Earlier that day, he arrived surprising his actor-self, who quickly appointed him for the great premiere of the movie because he “had business to attend to, plus it’s a pain”.

Said business turns out to be another man, shorter than him, who opens the door and greets him with a surprised face that turns into a confused smile. His rosy face is adorned on each side by strands of purple hair, and his eyes are of a similar color, brighter than anything Seishiro, the scientist, has ever seen before. He also recognizes the clothes the other man is wearing: his favorite sweatshirt and some shorts he has had for some years. It looks lowkey big on him.

He is beautiful.

“I can’t believe it” the man says.

But was he worth not attending your big life achievement?

Seishiro, the actor, appears behind his partner and grabs him from the waist to pull him inside. “I would never lie to Reo” he murmurs, and yawns.

The couple gets Nagi to sit on their couch and Reo walks around him, scanning his every angle, as if he could be an imitator or a crazy fan. The other Nagi just lies down, almost asleep.

“Are you really the Nagi Seishiro of another dimension?” Reo asks for the fifth time. Nagi doesn’t mind replying but he thinks that Reo is most likely trying to convince himself that everything was real.

“Where I come from it’s a couple of years in the future for both of you. Some theories were developed that explained the connections between parallel worlds and I have been putting them in practice.”

“Boring” actor-Nagi says and rolls around on his individual couch.

Reo doesn’t look like he thinks the same and very excitedly sits beside scientist-Nagi, who is startled for a moment because the mauve-haired man seems rather interested in him. Or maybe it’s because he looks like his boyfriend.

“Husband” Seishiro, the actor, corrects with a hand under his cheek. “We got married a year ago.”

“Today is our anniversary” Reo adds with a soft smile. “This alone will make it unforgettable.”

There are more questions exchanged until the late hours of the night, so much that it becomes early enough to go to work. The scientist should be one of those people. The actor has been asleep for almost an hour.

Reo wonders about the future of the country and the world, about the people, the economy and the wars. Then it becomes more personal as he wants to know about his family, if it’s the same as his partner’s, if both of them have a scar on their left knee from falling off the stairs as kids. They do.

“Am I there with you? In your world?” Reo finally asks and this Nagi has met him for less than a night and yet he can tell that he wanted to know that since the beginning.

“Not really. It’s my first time seeing you.” Reo smiles and nods a little. Of course that was one of the possible outcomes to his question. “How did we- How did you two meet?” The scientist questions him.

“We met in high school; I forced him to join the theater club after watching him present something for a class. Look where he got now.” Both look over at Nagi, the actor, who is just peacefully sleeping with a single cover that Reo brought for him earlier. “I didn’t have that much luck though, I had to take over my family’s business.”

“Who is your family?” The scientist asks, since he only knows this man by the name Reo but not his last name.

“Mikage, from the Mikage Corporation. Surely you have heard about it even in your world?” Reo jokes with a big smile.

The scientist’s eyes open a little more for a second, but he quickly controls the expression. “Barely, don’t know much about them. I’m always in my laboratory, you see.”

“Working on your experiments, got it. So… what is it? The dimensional-traveling machine, I mean. Will you show me? Does it look like an elevator like in that Spongebob episode where they travel through time? No, no, let me guess! Is it a car like in Back to the Future? Is it parked outside?” There are many questions once again and a somewhat childish excitement that comes from Reo which Nagi is not used to. “Oh, I know! Is it more subtle like a phone or a watch, right? If I know my husband, is that everything is a hassle, so you would prefer something easier to carry around.”

The scientist is speechless and a little touched. Reo smiles knowingly.

“I got it correct, huh?” and he winks playfully at him. It’s too much.

“It’s a door” Seishiro replies in a small voice.

“What door?” Reo looks around for anything that seems out of place in the apartment.

“Any door, as long as I do the right process. You won’t notice the difference.”

“I guess I am not invited to watch then, right?” Reo doesn’t stop smiling even after knowing that.

“I’m afraid so.” The scientist says as he gets up and goes to the bedroom. The door closes behind him.

After a couple of minutes of silence, Reo gets up and gets closer with short steps. He tries to catch any sign of light or sound that indicates that a portal is open and the moment he tries to get into his bedroom it will take him to a different world with flying cars, holographic products, and advanced robots that pass as humans.

He opens the door very excited.

And there is Nagi, the scientist, with a set of clothes he doesn’t recognize and the suit he was lent all over the floor.

“You both are so similar it’s kind of scary.” Reo buffs while closing the door behind him, and then walks in front of the other to pick up the dirty clothes. The scientist gets up. “Will we ever see you again?”

“I can’t choose where I go yet” Nagi reveals and walks to the door, opening it and walking through the umbral.

“Well, I hope you can find me in your world. Don’t you?” The door closes again. “Hey, that’s mean!” Reo says and walks over to follow after the traveler, he goes down the hallway and realizes that it is only him and his husband again.

 

 

Barou Shouei opens the door to Nagi’s office to find some documents. He sees the white-haired man sleeping on his chair, so he works quietly through a pile of books and paper until he realizes the stupid bitch has come back and starts to throw everything at him until he wakes up.

“What is your problem?” Nagi questions while trying to protect his face from the things that land on him very accurately.

“You came back and told no one, dumbass! Me and Isagi have been filling daily reports while following you on the dimensional map.” Barou seems genuinely exhausted, but his voice shows otherwise. Always loud and aggressive, Nagi thinks. What a pain. He is starting to fall asleep once more. “That means that I had to deal with Bachira Meguru for HOURS! This is all your fault!”

Isagi Yoichi storms inside the moment Nagi puts his head on the desk, eyes barely open. “Hey Nagi! If you come back you need to tell us immediately, I was so freaking scared when I couldn’t find you on the map and-”

“Don’t you dare fall asleep on us, idiot, I will kill you!” Barou takes an encyclopedia in his hands. It painfully finds its way to Nagi’s head.

Word spreads fast from there and his team receives the urgent message to join a meeting with the upper cabinet. It’s just one man named Ego Jinpachi but still, Barou and Isagi force Nagi to gulp some black coffee, then greet his members who were worried about his well-being, even though none of the travels has come out wrong so far, and all of them get in one of the floating, automatic vehicles that take them through the big installations where they work.

Yukimiya is on duty to report all that has happened around there for the last couple of days.

“In short, the machine was stable, and we never lost track of you. Also, Rin and Shidou were sent away for a couple of days because they fought over who broke the fridge while working on their projects.”

Bachira giggles at the mention of the incident and then adds “By the way, Nagicchi, your experiment has been revealed at one of those big and secret events with scary people. They are probably calling us to tell us about a co-program or something of the sort.”

“But did Ego really agree on that? He is very private and jealous about everything that happens here.” Chigiri mentions, his hair tied on a loose braid which also shows that they have been working non-stop in his absence.

“Must have been a very good deal.” Isagi comments and something inside Nagi seems to twist. He is probably hungry, and although he is a man of science and is always thinking with logic and reason, he still cannot leave behind his most human senses.

He feels like something is wrong-

“These are the representatives from the Mikage Corporation. They will work with you to design and apply a communication device that can resist the interdimensional jumps.” Ego says non-chalantly while pointing to a different group of people in the room. The one that caught Nagi’s attention the most has mauve hair and violet eyes that connect with his the whole time.

-and it really was.

“My name is Mikage Reo. It’s an honor to be working with you, Nagi Seishiro.” Reo bows and Nagi responds with the same gesture. There is a familiar smile painted on his lips.