"Hey, if any one of y'all want to go back to the past, lemme know. I'll kill y'all."

-From the records of [[Carpediem]]

Prologue. Carpediem

A sky hidden by the sky-soaring towers.

Various ruined structures. Faint sounds of moans and screams. Explosive smoke everywhere.

And continued silence.

Needless to say, this was the world after the apocalypse.

You all might know of this. I will not go into the details, but you will understand once you read the history.

Year 2018.

Enormous structures, or the [[Tower of Nightmares]], appeared in the skies of various cities around the world, including Seoul.

…I just realized it's a ton of work to go through every date. Besides, there are all sorts of similar fantasy novels that consist of similar stories, and that makes me wonder if I even need to explain everything.

But this'll make it simpler, so I'll continue on for a bit.

I should at least explain why mankind reached such an end.

As you might know, the beginning was calm.

In 2018, an enormous structure called the [[Tower of Nightmares]] appeared in the sky above the city. The tower did not state anything nor did it explain itself, but the humans began talking. There were rumors and speculations that the end had come.

Then the tower called upon humankind.

[[Tower Walkers]]

The ones who were later referred to as Walkers.

These people were summoned by the tower's 'message' and they had earned the power and right to climb it. This was the message: 'Accept the summon if you want to stop the extinction of mankind.' And thousands of people responded to it.

It was about a ten thousand to one ratio if one considered the entire population, but it was still fortunate. There were that many people who were willing to do what it took to save mankind.

But the information extracted from the Tower of Nightmares showed various rewards for climbing up the tower, which probably had attracted a lot of people too.

Anyway, these people then received the power called the [[Interface System]] that allowed them to earn items and skills just like a game to climb up the Tower of Nightmares.

People were not so eager to climb, however. There was the possibility of encountering various dangers and the human extinction that the tower mentioned was also very vague.

That was when the First Tower Impact occurred.

The tower let some monsters loose to kill the inhabitants below, killing one-third of the Earth's population.

Now, you might know what happened afterward.

Those Walkers were given an important task to climb up the tower for the sake of humanity.

But this story full of clichés does not end here.

Year 2023

A revival item, [Returning Stone], was found.

Just like the name said, it worked exactly as indicated.

Now you'll know what this story is about. Yes, it's a story that everyone might know.

Just when the world was about to end, the main character accidentally found the item that would take him back to the past.

With the discovery of the [Returning Stone], there came the truth behind the story that might've only existed in novels.

Time traveling back to the past.

It was a good thing, but there was a problem.

"Dammit! I'll just go back then!"

"Yeah! We're screwed this time!"

"Me too!"

"F*ck it! Me too!"

Too many had gone back to the past.

Jaehwan spoke as he saw a group of people turning into light as they disappeared.

"There they go again…"

"…"

"Is that the last of them?"

"Probably."

Yoonhwan answered as he watched them. They were watching those lights disappearing from the 98th floor of the tower.

Those lights that disappeared through the sky were as beautiful as meteors.

The light that had hope on the new life of the past.

They would now forget every hour they spent in this ruin and start life anew in the peaceful past.

The safe, peaceful life that everyone once knew.

"Good."

"No way."

Jaehwan understood why people would want to go back to the past.

They all probably had their own stories.

Everyone would've wanted to become the 'main character' of the world.

But it made Jaehwan wonder.

Did they even think about it once? The fate of people who would continue to live in the world that they had abandoned?

It had been 10 years since the discovery of the [Returning Stone]. Other than the Walkers who were killed, all the remaining Walkers went back. Thousands of them gave up on the chance to save mankind and returned to the past.

The [Returning Stone] was the reward on the 77th floor.

It was a giant stone that blocked the pathway to the 78th floor.

Everyone later realized that this giant stone was actually an item.

The item had the following properties:

[Item Details]

Name: Returning Stone

Rank: Legendary

Description: Sends the user back to the past when the user was summoned. The user's memory stays intact. The stone is broken into pieces for use.

Nobody believed it at first. Although the items that the tower gave were fascinating, it seemed too good to be true.

But people were tempted.

These Walkers were those who had experienced various supernatural phenomenon in the tower. But most Walkers were without skills or the items they sought. These kinds of Walkers were tempted.

Start all over again with every piece of knowledge they'd acquired?

"If we can break it down to pieces… everyone probably can take it!"

The first one who used the stone was Sword Panic, or Hwang Inchan, the leader of the front-line adventure group [[Blade Walker]].

"It might be fake so I'll test it beforehand and let you know."

And that was his last words. Jaehwan was there when he said it.

'Everyone was fooled.'

It didn't make sense. If it really took him back to the past, then there was no way for him to come back to let everyone else know.

But it was enough to make people panic.

"Is it true? Did he really go to the past?"

Some were skeptical but there were a lot who took the pieces for themselves. Inchan never returned.

Thus, the people were curious.

Why isn't he reappearing in this world? Why is the world still the same?

The answer came from the team's sole Japanese member and the middle-school's science teacher Sakamoto.

"Maybe it's only natural."

He explained the multi-universe theory and the parallel universe theory, going through the possible outcomes. According to some theories, it seemed that their history probably had parted ways from Inchan's world.

"Inchan must have returned successfully, but the world he returned to had divided into another route where we will never meet him again."

Most of the people were not very science-literate so they couldn't understand much.

But two things were certain.

One was that Inchan did return to the past, and him going to the past did not change the current world.

"Hey, is there a possibility that Inchan was transferred to elsewhere?"

"Look at the description on the stone. As far as I know, item descriptions have displayed any lies to this date."

What Sakamoto said was true.

"I think it will send us all back to the world, but its all theoretical so we can never be sure."

And like that, half of the leading expedition team went back to the past. If they were to fall into the same time period as others, they wanted to be a step ahead and be top of the others who had also gone back to the past.

That was when mankind began yearning for 'time travel to the past.'

Everyone began thinking about what to do if they returned to the past.

There were some who thought it'd be better to go back faster while others thought it was better to try getting to the higher floors beforehand. There were some who even took advantage of the stones and sold it to the Walkers on the lower floors.

Then, the Second Tower Impact occurred.

It was the disaster that unleashed terrible monsters from the towers to the ground. It killed almost all of mankind except Walkers who were on the tower.

The Walkers were left with one of two choices.

Pay whatever it takes to get their hands on the [Returning Stone] to go to the past, or stay and die. But Jaehwan chose neither of the options.

"Damn idiots. Stop going! What will become of this world if you all go?"

Even with the best, front-line team [[Blade Walker]]'s dismantle, Jaehwan and a few of his friends proceeded further to higher floors.

Then they were stuck on the 85th floor. Most of Jaehwan's friends were killed. There was no going forward.

Jaehwan began persuading and training other Walkers coming from below. He handpicked individuals who might not be tempted by the [Returning Stone].

The final assault team [Carpediem] was created.

The final team that stayed behind to protect the world.

Jaehwan led the team and broke through the 85th floor.

They went up and up.

There were some casualties and some went back to the past.

But they persevered.

And so, they reached the 98th floor.

Jaehwan blamed the Walkers who returned to the past. If even half of them stayed, the world would not have ended this way. Even after multiple tower impacts, mankind persevered. Many were dead and wounded, but they still somehow managed.

But they were at the limit.

Only two [Carpediem] members remained.

Jaehwan did not give up.

"Let's go, Yoonhwan."

As far as he knew, the 100th floor was the tower's last floor.

There were only two more floors.

Two more floors until the end of this hellish age.

The humankind would be freed. The world would be given another chance.

Or that's what Jaehwan thought. Or what he believed.

"Yoonhwan?"

No answer.

"Hey."

One of the final members. Smile Knight, Kim Yoonhwan.

He smiled even during the worst times, and thus the members gave him such a name. But he wasn't smiling now.

"Wait…"

Where did he get the stone? Jaehwan glanced at the small stone that Yoonhwan was holding.

"You… are you going to the past also?"

He couldn't believe it. Yoonhwan lowered his head and Jaehwan tried to jump at him, but he suddenly turned his back on him.

"…Go."

"I'm sorry, Jaehwan."

"Go away. Before I change my mind."

Jaehwan walked toward the gate to the 99th floor while Yoonhwan watched his back.

It had been the back that he followed all the way here.

The gate opened and Jaehwan walked in. As he disappeared, Yoonhwan staggered and set himself up against the pillar of the tower.

His breath began to grow heavy as blood streaked down between his clothes.

There was a small hole around Yoonhwan's chest.

It was the wound from the boss monster, Giltikas.

It wasn't something that a mere potion could heal. Only a rare-ranked Priest would be able to heal it but there were no more Priests left in this world. His best friend would have noticed the stone he was holding wasn't a [Returning Stone] immediately. Yoonhwan tightly held onto the stone. He felt the cold, rough edges. It was something he could only feel in this world.

He had learned this from Jaehwan.

He had learned how to clutch this rough, worthless life and never let it go.

But it was time to let it go.

Yoonhwan walked to the edge of the tower and stood there.

"It was nice to have known you, Jaehwan."

Then his body disappeared off to the clouds and Jaehwan stopped as he opened the gate to the 99th floor. He used his right hand to wipe off his face. He waited until he stopped shivering and started to calmly breathe again. But he did not look back. He walked up toward 99th floor alone.

His world was not yet finished.