At first, Dr. Jeong Ki-hoon thought there was an error in the initial data input into the simulation.

“Did I input the data incorrectly?”

He reset the settings and ran the simulation again. Still, the result did not change.

“If I run a proper simulation after returning to the lab…”

Jessica asked from beside him.

“Dad, why do you look so serious?”

“Something seems wrong. It was supposed to be wrong.”

Jeong Ki-hoon rechecked the formula and reviewed the necessary information.

“This really makes no sense, why is the result coming out correctly?”

Even though the formula had been modified, the results still came out correctly. It was slightly different compared to when he simulated his originally published formula, but not enough to definitively declare which one was correct.

Jessica offered her opinion.

“Maybe Detective Seo copied it from somewhere?”

“That’s impossible.”

This theory was led and researched by Jeong Ki-hoon himself. It had only been published in an international journal a few days ago, so there was almost no chance another lab had analyzed it and published a modified formula already. Even if someone had, Jeong Ki-hoon would have known before Seo Jung-woo.

Seo Jung-woo did not modify the formula in this world. He brought the complete formula from the other world’s Dr. Jeong Ki-hoon.

Jeong Ki-hoon checked the time. There were still ten hours left of flight time.

“I need to properly analyze this modified formula.”

His expression was grave.

The hotel that Seo Jung-woo arrived at was deep in the mountains, quite a distance away from Gangneung.

The sea was not visible from there. Instead, tall mountains surrounded the place in all directions. The road was rough, so even by car, it would take a long time to reach Gangneung.

He booked a room at the hotel.

At the front desk, the staff checked his ID and hesitated.

“Oh my. Are you perhaps Detective Seo Jung-woo who appeared on the news?”

“Ah. Yes.”

“H-How come you're here? Oh! I'm a fan!”

“Huh? A fan of a police officer?”

Suddenly, the staff's expression stiffened.

“Ah! C-Could it be that there are international terrorists in our hotel…”

“No. Things have been a bit noisy lately, so I came to spend some quiet time. I'd appreciate it if no rumors spread.”

“Huh? Oh! Of course!”

Seo Jung-woo ate at the hotel restaurant and then went up to his room. After a while, room service delivered wine and snacks.

“I didn't order this.”

The hotel staff smiled.

“It’s a gift from our manager to Detective Seo Jung-woo.”

“Ah. It's free, then. Thank you.”

Although he asked the desk to keep quiet, he anticipated that word would spread among the staff.

‘Just as I thought.’

After the staff left, he only ate the snacks while organizing his thoughts.

‘Everyone at the hotel probably knows I'm here by now. I must have been caught on CCTV when I arrived. Records of my vehicle passing through the highway tollgate would also remain.’

The reuse cooldown for the parallel dimension teleport skill was 24 hours. Since he used it last night, he could only use it again tonight. However, tonight was not the right time.

He showered and then lay down on the bed. Having stayed up all night, he needed some rest now.

“Let's leave early tomorrow morning. That would look more natural to others.”

Dr. Jeong Ki-hoon spent the entire flight over the Pacific without sleeping, immersed in verifying the formula. Since he originally led the creation of the theory, verifying the modified version wasn't too difficult.

He finished his work just as the plane crossed the Pacific into American airspace.

“This is…”

Jessica, who had slept soundly, stretched and asked.

“Dad, did you stay up all night? Did you find the mistake in the modified formula?”

“The problem is that there's no mistake. This can't be happening.”

Seo Jung-woo woke up early the next morning and checked his weapons. After that, he checked his phone. He had kept it on all night to leave a location trace, but had silenced both the sound and vibration.

The phone had several missed calls and messages.

As he was about to put the phone down, a call came in.

It was an unknown number. He was about to ignore it like the others but changed his mind.

‘Maybe I should make it a little more known that I'm here.’

“Hello.”

Soon, Dr. Jeong Ki-hoon's shouting voice burst out loudly.

- What is going on here!

“Dr. Jeong? Looks like you’ve arrived in America.”

- What did you do with this formula?

“It shouldn’t be strange.”

- No, the strange thing is my original theory! While verifying the formula you gave me, I discovered an error in my own theory. The formula you gave me is correct. So how did you come up with it!

The Dr. Jeong Ki-hoon in the other world had published an erroneous theory and suffered a great deal of embarrassment a month later. Seo Jung-woo had obtained the corrected formula while he was there.

But he couldn't explain that.

“That’s lucky. I just wrote down a thought that popped into my head, that’s all.”

- Does that make any sense!

“It does.”

- Where are you now?

“Since a lot of people were looking for me, I came to a quiet hotel in Gangwon Province to rest.”

- Then please find a place with a computer connected to the internet. We must have a video conference to discuss this theory…

Seo Jung-woo quickly interrupted him.

“I only know the basics of physics, so please don't ask me anything deep. I really don’t know anything.”

It was true. He only knew the basics and his understanding was shallow. He had helped a little because he had fought alongside Dr. Jeong Ki-hoon a few days ago and knew that even now, Dr. Jeong Ki-hoon in the other world would kick his blankets whenever he thought about the mistake.

If a serious discussion about the formula began, his lack of knowledge would be exposed immediately. That had to be avoided.

Dr. Jeong Ki-hoon protested in a flustered voice.

- No! How is this just basics…

Seo Jung-woo immediately hung up.

“You should just accept the gift quietly, why dig further? I really don’t know anything.”

He slung his backpack over his shoulder and went down to the front desk. A staff member asked him.

“Oh my, you're leaving early.”

“I plan to spend today feeling nature in the mountains and return here tomorrow morning.”

“Ah, so Detective Seo's incredible martial arts skills were honed while training in the mountains of Gangwon-do?”

“Yeah, something like that. Ah, I have to leave my car in the parking lot. How about the parking fee?”

“We’ve received instructions to provide Detective Seo Jung-woo with top-class service. Of course, parking is complimentary.”

“Thank you.”

After finishing the call with Seo Jung-woo, Dr. Jeong Ki-hoon fell into deep thought.

“How did Detective Seo find the error so quickly? Even our team and the journal that published the formula didn’t notice any issues.”

Moreover, that journal had only been published a few days ago.

“Since he was assigned as my bodyguard the day I requested it, he wouldn’t have known the theory in advance. Even if he did, it would’ve been only a day or two earlier. If he first learned about it while guarding me that day by seeing my presentation... he wouldn’t have had the time to find the mistake. He spent the day guarding me, drinking with me, rescuing Jessica, and explaining the situation to various organizations. How on earth did this happen?”

He couldn’t understand it at all.

Jessica asked,

“Dad, what’s wrong?”

“No matter how much of a genius someone is, this defies common sense. Why on earth is someone like him a detective? He should obviously be a scientist.”

“You’re talking about Detective Seo?”

“Yeah.”

“Where is he now?”

“He said he went to rest at some hotel in Gangwon-do.”

Jessica said regretfully,

“Tch. I should’ve come a few days later. Then I could have followed him.”

“Huh? No, that’s a bit...”

Seo Jung-woo entered the mountain right in front of the hotel. He deliberately headed into rough, unmarked terrain, and soon lost cell phone signal.

“Perfect.”

Checking his watch, he saw only 20 minutes had passed since he left the hotel.

He checked the surroundings. There was no one else deep in this mountain.

He opened his backpack and took out a pistol loaded with armor-piercing rounds. He disengaged the safety and set the firing mode to automatic. Holding the pistol in his right hand and the bag in his left, he left the zipper open so he could quickly draw additional weapons.

Then, he used his parallel dimension teleportation skill.

The scenery before his eyes changed drastically.

He immediately raised his pistol and scanned the surroundings. He didn’t sense any monster bloodlust.

Still, he couldn’t let his guard down. It could just be that the monsters hadn't spotted him yet.

‘In this world, gate cleanups often aren’t thorough.’

In countries with vast territories and sparse populations, gates often weren’t properly managed, leaving significant areas occupied by monsters.

Meanwhile, Korea, thanks to strong military power and high population density, immediately deployed the military or hunter teams to eliminate gates nationwide. Large-scale gates like the Jeokseong Gate in northern Gyeonggi were a different story, but the principle was to eliminate small and medium ones as quickly as possible.

However, in rough mountain terrain like this, gate discovery itself could be delayed. Monsters escaping before a gate closed would sometimes hide in the mountains. So if you wandered into the mountains carelessly, you might encounter leftover monsters.

“At least there shouldn’t be any large monsters.”

Large monsters are easily discovered because they can’t hide between the trees. Some medium-sized ones could burrow underground to hide, but such monsters rarely remained as stragglers.

Usually, only small monsters roamed such places. And most small monsters could be taken down with armor-piercing rounds.

Seo Jung-woo trekked through the mountain toward Gangneung. The terrain was rough and the forest dense, so even with detection skills, he had to stay vigilant.

After three hours of climbing, he finally arrived at an airfield in Gangneung. There, he called a soldier from the awakened special forces unit.

- Huh? This number belongs to Seo Jung-woo. Is that really you?

“Yeah, it’s me, Captain Yoon.”

- Wow, it’s rare for you to call first. But hey, shouldn’t you stop calling me Captain? I’ve been a lieutenant colonel for a while now.

“Considering your age, you were promoted way too fast. Captain suits you better.”

- If you hadn't left the military, you’d be wearing a star by now.

“You know I grabbed all the guys trying to chain me to the army by the collar and shook them, yet you still bring that up?”

- Hey, I’m just kidding. I almost broke my neck back then. Anyway, where are you? Let’s grab a drink for old times' sake.

“I’m at the Gangneung Air Base.”

- Huh? Ah, that explains why you’re calling. Why are you there? Flying somewhere?

“I’ve got business in Japan.”

- Ah, there are military transport flights to Japan from there every day.

Flights to China departed from Incheon Airport, while flights to Japan left from Gangneung and Busan to save on aviation fuel and reduce the risk of attacks by flying monsters.

“Hey, can you get me a seat on the flight to Japan?”

- I can make a seat, but…

Lieutenant Colonel Yoon Hyun-sik hesitated before asking,

- Are you planning to blow something up in Japan? If the mess gets too big, it could cause a diplomatic incident.

“I’m just going for sightseeing.”

- Sightseeing? Hitching a ride on a military transport to go sightseeing? You expect me to believe that?

“I’m not going to shoot anyone over there.”

At least, not in this world where gates were opening. His real target was the remnants of an international industrial spy organization in the other world.

- If you only shoot a few, we can cover it up. Just keep it under ten people.

“Stop fishing for information. I said I’m not going to shoot.”

- You’ll need a round-trip ticket, right? You’ll come back?

“Of course.”

- How long?

“One day.”

- If it's just a day, you probably won’t cause too much trouble. Hmm. But you know, you can’t get it for free, right? And not with money either. It’s a military transport, after all.

“What do you want?”

- Our unit has a mission coming up. Be an observer for us.

“And intervene if it gets dangerous?”

- Exactly.

“Sounds like you’re expecting trouble already.”

- Hahaha.

“How much is the observer fee?”

- I’ll make sure it’s generous. We’ve got a fat budget.

“Deal.”

- Deal.