By extracting special substances from certain monsters and refining them with human technology, an excellent wound-healing medicine can be created.

However, this special substance cannot be extracted from all monsters, nor can it be harvested in large quantities at once.

To address this, pharmaceutical companies mixed the extracted substance into their medicines to increase the production volume of healing agents.

Each company had different substances, proportions, and processing methods, but the wound-healing effects of these medicines far surpassed those of the other world.

Among these special substances, some were even rarer. Monsters possessing such rare substances were significantly stronger than their counterparts.

When refined using human technology, this rare substance could be turned into a red liquid medicine.

People called it the Red Potion.

With the Red Potion, even wounds where the stomach was pierced or the chest was slashed open could be healed. Even severed limbs could be reattached simply by aligning the cut and applying the Red Potion.

The healing effects of the Red Potion were so miraculous that they could only be described as a miracle.

For hunters, the Red Potion was essentially an extra life. However, due to the scarcity of its ingredients, its production volume was extremely low.

With high demand and low supply, the price naturally skyrocketed. While the Red Potion was available for purchase, it was incredibly expensive and rarely found on the market.

Seo Jung-woo had once used the Red Potion to save Park Cheol-woo.

Seo Jung-woo handed Park Cheol-woo the recorded file of the song sung by 4Cats.

“Help me with this. I'll try to get my hands on a Red Potion.”

“Huh? Are you serious? You’re really going to get a Red Potion?”

“If you die, I’ll be in a lot of trouble.”

Park Cheol-woo smiled as he played the recording.

“I told you, I’m not planning on dying anytime soon.”

He listened to the song from start to finish, then clicked his tongue.

“Tsk. These kids didn’t quite understand my advice this time.”

“Since one of the four is an idiot, write it down more clearly and kindly.”

“By the way, are they actually debuted? I couldn’t find their song anywhere when I searched.”

“Uh… It’s complicated. You won’t find it even if you search.”

There was no way it would appear in a search in this world.

Park Cheol-woo didn’t press for more details.

“Well, everyone has their own circumstances.”

He pointed out specific things 4Cats needed to pay attention to while singing.

After returning to this world, Seo Jung-woo organized Park Cheol-woo’s advice and sent an email to Seo Sora.

The four members of 4Cats gathered in front of the monitor and read the email together.

Yoon Nana was amazed.

“Wow, Sora. Your brother is really kind. Every sentence is filled with warmth. Is he always this sweet?”

Seo Sora crossed her arms.

“No. Absolutely not. Don’t be fooled.”

Park Ha-yeon raised both hands.

“Detective D, we reve—”

“Stop! Don’t do that ‘reverence’ thing!”

Park Da-yeon urged.

“Let’s hurry up and practice! Practice!”

A few more days passed.

Every time Seo Jung-woo traveled to the parallel dimension, he met with Park Cheol-woo for advice and relayed it back to 4Cats upon his return.

On the day of the radio broadcast, Park Cheol-woo listened to the recorded file and gave his approval.

“This should be good enough to avoid embarrassment.”

4Cats was nervous.

Yoon Nana was worried.

“We’re going on a radio show tonight, but what if they still say we’re not ready?”

Park Ha-yeon shouted confidently.

“Unnie, don’t worry! We really nailed it this time!”

Park Da-yeon agreed.

“Yeah! This is our best!”

“Even if we practice more, we won’t improve much!”

“You have to know when to be satisfied!”

Yoon Nana glared at the twins.

“You two! Are you showing off just because you got praised?”

The twins nodded in unison.

“Unnie, if you’re jealous, just say so.”

“Our talent is top-tier.”

“That’s only because Detective D gave such detailed advice on your parts!”

It wasn’t intentional on Seo Jung-woo’s part. Park Cheol-woo openly favored the twins, giving them advice that was three to four times longer than what he gave to Seo Sora or Yoon Nana.

Seo Sora’s smartphone vibrated on the table. Instead of a name, the caller ID simply displayed ‘Oppa.’

Yoon Nana quickly reached out and put the call on speakerphone, her eyes shining with anticipation.

Seo Sora shot Yoon Nana a glare before speaking into the phone.

“Yeah, Oppa.”

– Fold your hands and listen respectfully.

“Shut up. How’s our song? Huh?”

– You won’t embarrass yourselves on the radio today.

Suddenly, Yoon Nana screamed.

“Kyaaah! Thank you so much!”

Seo Jung-woo’s voice carried a hint of surprise.

– Huh? Who’s… Ah. Speakerphone again.

“It’s me, Nana!”

The twins quickly chimed in.

“I’m Ha-yeon!”

“I’m Da-yeon!”

– Ah… Oh! There’s the criminal! Stop right there!

The call abruptly ended.

The twins high-fived each other.

“Yes! We passed!”

“Mission complete!”

Yoon Nana sighed in relief.

“Whew. Thank goodness. Now we can go on the show and sing without worries.”

4Cats waited in a small waiting room at the radio station for the PD to call them in.

Yoon Nana had been shaking her leg nervously for a while.

Seo Sora pressed down on her leg.

“Nana! You said you weren’t worried anymore!”

“I didn’t realize live broadcasting would feel this different from practice.”

“It’s the same. Just answer the questions and sing when they ask. That’s it.”

“Sora.”

“What?”

“Is Detective D coming?”

“Why would Oppa come here?”

“If he did, I’d really feel at ease.”

“Well, he is coming.”

Yoon Nana’s eyes widened. She stopped shaking her leg and grabbed Seo Sora’s hand.

“Seriously? He’s really coming?”

“Not here. We’re meeting outside after the show for a late dinner.”

“Wow! Is Detective D treating us for our first broadcast?”

“No.”

“Huh?”

“You heard him say we have to buy chicken as soon as we get paid. He’s just coming to eat that. Isn’t it too much for someone with a salary?”

Yoon Nana looked slightly flustered.

“Wait, the payment comes today?”

“Huh? It doesn’t come out today?”

Neither of them knew. Today was their first broadcast.

“I don’t think they’d hand it to us in an envelope right away.”

“This is bad. If we don’t buy him chicken, oppa will definitely sulk again.”

Yoon Nana’s eyes sparkled.

“I have money. I can buy chicken.”

“Huh?”

“I’ll go with you and buy it!”

The twins caught on to the situation and shouted.

“Unnie! We got our allowance too!”

“We’ll buy the beer!”

Seo Sora shut it down immediately.

“Minors buying beer? Our oppa is a cop. You think he’d allow that?”

“Then we’ll get cola!”

“Include us too!”

After a brief squabble, their nerves eased. Yoon Nana was no longer shaking her legs.

Moments later, 4cats entered the radio studio as guests. After a brief greeting and introduction, the four sang If We Can Meet Again.

When the song ended, the host was impressed.

“That was a really great song. At first, I thought it was just a cheerful tune, but by the end, it left me with a strange sense of nostalgia.”

Outside the studio, the PD made a circle with his fingers. It meant the message board reactions were fantastic.

Seo Jung-woo sat on a bench, listening to the radio on his smartphone.

“They’re singing even better than when they released the digital single.”

As he listened to the broadcast, he also checked the posts flooding the message board.

“The reactions are good too.”

The bench was right in front of the broadcasting station building. Listening to the music while looking at the building felt surreal.

“Seeing that building still standing…”

During the Yeouido defense battle, he had entered that very building to rescue trapped people. It was a dangerous mission—he infiltrated an area swarming with monsters, bringing survivors out alone.

Among those he saved back then was actress Lee Sun-hwa.

“I looked her up online, and in this world, Lee Sun-hwa is a top star.”

The same people existed in both worlds, but they had spent nearly twenty years in completely different environments. Their fates had diverged significantly.

A man talking on the phone walked past him.

“You want me to arrest Detective Seo Jung-woo? That’s not it, right? You just want the interview, so why can’t you even do that?!”

The man yelled into his phone.

“What? He never does interviews? Then what about those news briefings? Forget it. If you can’t get an interview with Seo Jung-woo, don’t even think about coming back!”

He was shouting into the phone when he suddenly froze.

‘Huh? I think I just saw Seo Jung-woo.’

He had watched Seo Jung-woo’s press conferences and seen his photos many times.

With a broad smile, he turned toward the bench.

“Ah! Detective Seo Jung-woo—”

The bench was empty.

“Huh?”

He quickly looked around, but Seo Jung-woo had already disappeared.

He rubbed his eyes.

“Wow. Am I so desperate for an interview that I’m seeing things now?”

The radio host spoke to 4cats.

“I hear you’ll be premiering a new song here today. I’m looking forward to it.”

Seo Jung-woo moved to a new location and checked the radio show’s message board.

– The first song just came out. Why are they releasing a new one already?

– Wasn’t the first one rushed out just to ride the kidnapping incident?

– It wasn’t rushed. If We Can Meet Again is a high-quality song.

– I can accept one good song by chance. But a second digital single so soon?

– Looks like they’re rowing while the tide is high.

– No matter how good the song is, they can’t perform at events with just one song. You need at least three. Let’s cut them some slack.

– I get it, but this still seems off.

4cats began singing their second song, Smash It.

The radio host personally liked If We Can Meet Again. He had listened to it often.

But this second song was entirely new to him.

His earlier comment—"I’m looking forward to it"—was just politeness. He wasn’t expecting much.

‘There’s no way a failing company like ES Entertainment could get two good songs in a row. Unless Oh Dong-cheol’s throat wound miraculously healed and he got his old voice back. And even if that happened, the song would go to Oh Dong-cheol, not a rookie group…’

As soon as the singing started, his thoughts vanished.

‘Huh?’

Though it was his first time hearing the song, his shoulders naturally started moving. It was exhilarating.

‘This is…’

“Amazing.”

He spoke without realizing it and quickly shut his mouth, remembering they were in the middle of a performance. Luckily, his mic was off. He let out a relieved sigh.

4cats poured all their energy into the song for nearly four minutes. When they finished, they sat back down, looking satisfied.

The host turned his mic on and spoke.

“That was fantastic. Wow, what an exciting song.”

The four members bowed their heads.

“Thank you!”

The host smiled.

“No, thank you. That was an amazing performance.”

The message board was exploding with posts.

– Whoa, amazing!

– This song has a completely different vibe from the last one, but it’s so good.

– Who was the one who said we should be understanding even if the song was bad?!

– I take it back!

The host asked, “What exactly are you smashing in this song?”

Yoon Nana answered, “I think it means breaking the barriers that hold us back.”

– The energy! I can feel it!

– This feels like a fusion of dance and rock, but either way, WAAAAH!

– Me too, WAAAAAH!

Originally, the lyrics were meant literally—to smash real monsters.

But since there were no monsters in this world, Yoon Nana interpreted “monsters” as prejudices, societal expectations, and rigid traditions.

The host asked, “I see that the composer is listed as Dimension. That’s the same person who wrote If We Can Meet Again, right?”

The four members answered in unison.

“Yes!”

“It’s possible to get lucky with one good song. But to write two incredible songs? That’s not luck, that’s skill.”

Yoon Nana beamed.

“Yes! He’s truly amazing!”

Then, the host dropped a sensitive question, live on air.

“So, who exactly is this person?”

“Huh?”

“I’m starting to wonder if he might be someone well-known.”