Haizaki opened his eyes and saw a clear blue sky and a dazzling sun.
A faint smile appeared on his face, his expression unable to hide his excitement.
He really had come back.
How wonderful.
Haizaki greedily inhaled the fresh air mixed with the faint fragrance of cherry blossoms.
This was the scent of sunlight—the breath of peace.
Cherry trees swayed gently in the wind as pink petals drifted down. On the street, students walked toward school in small groups. High school girls in black pleated skirts looked youthful and vibrant, their figures full of life.
Haizaki was an exchange student from the Eastern Union who had transferred to Chiba Prefectural Sōbu High School as a second-year student.
Today was April 1st—the first day of the new school year for Japanese high schools, and also the season when cherry blossoms were in full bloom.
Aside from Haizaki, no one knew that he came from a ruined, apocalyptic world two years in the future.
Two years later, on the day of Sōbu High's graduation ceremony, the world would undergo a sudden and catastrophic change.
What followed was a world filled with death and decay. The air reeked of gunpowder and blood, the sky was perpetually gray, heavy with oppression and despair.
Humanity was driven to extinction. Civilization reached its end.
And in the end, he had been forced to traverse time itself, returning to the most special day of his life.
...
"Haizaki-san, the school has informed me of your situation. I hope you'll cherish this opportunity, study hard, and aim to get into the University of Tokyo, bringing honor to Sōbu High. If you encounter any problems in your studies or daily life, feel free to contact me."
"I understand, teacher. I'll study hard and won't disappoint the school."
When Haizaki was in his first year of high school in the Eastern Union, he transferred into Sōbu High's second year as a specially admitted academic student.
He lived up to that status.
He focused on his studies, handled matters seriously, kept his distance from the opposite sex, and earned admission to the University of Tokyo with outstanding grades.
Yet who could have imagined that before that beautiful university life could even begin, a cruel new era would arrive?
Everything he once pursued became an illusion—fragile as bubbles—shattered completely and rendered meaningless.
"Excuse me, teacher."
Haizaki gestured in farewell and carefully closed the office door behind him. Every movement reflected proper etiquette, which left the homeroom teacher of Class 2–J, Yamada, very satisfied.
"Thud—"
As Haizaki turned and took his first step forward, he unexpectedly bumped into someone.
He hurriedly reached out to steady the person who had lost her balance and was about to fall.
Slender. Soft. And carrying a faint, sweet fragrance.
Without a doubt, it was a girl. Yet beneath that delicate scent was a trace of coldness that felt strangely familiar.
"I'm sorry—"
Haizaki lifted his head, and what he saw was a familiar, cool-looking girl.
Just as in his memories: a dignified presence, long black hair falling past her shoulders, fair skin, an irresistibly cute face, crystal-clear features like freshly fallen snow. Her black school uniform paired with slender black stockings fully displayed her youthful beauty.
Seeing her again, Haizaki felt conflicted.
Only after losing something does one truly understand its value.
"Yukinoshita Yukino…"
His classmate—the famous "Ice Queen" of Sōbu High, and the head of the Service Club.
And… strictly speaking, his first love—if one counts the first girl he ever secretly admired.
In his previous life, the moment he transferred to Sōbu High and saw Yukino for the first time, he unconsciously developed feelings for her. It was love at first sight, one could say. Yet like most boys, he kept that faint affection buried in his heart.
He understood that his background and abilities were insufficient to provide her with material happiness.
Rather than clinging to unrealistic hopes and indulging in empty fantasies, it was better to stop there.
He would wait for high school to end and allow those feelings to fade with time.
"You can let go now, classmate."
The girl's cool voice reached Haizaki's ears.
"Alright."
Yukino glanced at Haizaki, her clear eyes seeming to confirm whether his actions had been intentional.
"Please be more careful in the future."
"Yes, I will."
Cherry blossom petals drifted into the hallway with the breeze—fresh and romantic.
They passed each other.
From the corner of his eye, Haizaki glanced at the girl beside him. The scene of their parting before the apocalypse erupted resurfaced vividly in his mind, as though it had happened just yesterday.
The emotions hidden in her dark blue eyes—confirmation, pleading, longing—were all mixed together. Yet he had failed to respond in time.
By the time he resolved himself and chased after her, all that remained was an empty street. The girl was already gone.
"It won't happen again…"
The faint whisper reached Yukino's ears, causing her to pause. Her gaze instinctively shifted toward Haizaki, whom she had just passed.
Something felt off.
A strange man.
That was the thought that crossed Yukino's mind.
...
"Now, the exchange student from the Eastern Union, Haizaki-san, please introduce yourself."
"I'm Yusuke Haizaki. Nice to meet you, everyone."
Familiar yet unfamiliar faces—everyone was still alive. The feeling was truly wonderful.
All eyes in the classroom focused on the new student.
"Let's welcome Haizaki-san to our class—"
The homeroom teacher of Class 2–J, Mr. Yamada, raised his hand, signaling for the students to quiet down.
"Haizaki-san, please take that seat over there."
"Yes, teacher."
Haizaki walked toward the last seat by the window. Sitting in front of him was the very girl he had just encountered—Yukinoshita Yukino.
Haizaki nodded slightly at her in greeting.
Yukino looked back at him, her expression as cool and indifferent as ever. However, inwardly, she felt a hint of surprise.
Why did Haizaki, the transfer student from the Eastern Union, know her name?
Though puzzled, her personality meant she would not ask proactively.
Haizaki, meanwhile, focused all his attention on the sound that was about to appear.
One minute left.
It was time.
"Beep—beep—beep…"
Hearing the notification sound, Haizaki's lips curved upward. Everything was just as he remembered.
"Personnel selection complete. The 'Trans-Spatiotemporal Human Civilization Salvation System' is initiating binding. Do you wish to bind?"
"Yes."
Haizaki silently chose yes in his heart.
In his previous life, on this same day—April 1st—he had also heard this mechanical voice. However, out of caution, he had chosen "No."
After that, he never heard the strange mechanical voice again. Naturally, he assumed it had been an auditory hallucination and soon forgot about it.
Until two years later, when the world was overturned and the apocalypse descended, the mechanical voice sounded once more.
But by then, due to the drastic population loss and severe damage to the "Principles of Human Civilization," the Trans-Spatiotemporal Human Civilization Salvation System had lost nearly all of its functions.
He had missed a chance to save human civilization.
Originally… perhaps so many people wouldn't have had to die.
"Binding successful."
"Hello."
"I am the auxiliary spirit of the 'Trans-Spatiotemporal Human Civilization Salvation System.'"
"At your service."
Haizaki immediately asked,
"I need information related to the 'Trans-Spatiotemporal Human Civilization Salvation System.'"
"The Trans-Spatiotemporal Human Civilization Salvation System is dedicated to redeeming human civilization and delaying or preventing its destruction. System users will travel to one apocalyptic world after another, complete missions, and obtain rewards in order to ultimately save the human civilization of their own world."
So the method was to explore other worlds in order to find a way to save his own.
"The time of the next entry into an apocalyptic world?"
"This world, Tokyo time, April 2nd, 2019, at 00:00."
Fifteen hours left. There wasn't much time.
"What worlds are currently available?"
"The only accessible apocalyptic world at present is 'Solitary Apocalypse.'"
"Can I bring people or items?"
"Beginner-level D-rank users may carry up to ten kilograms of supplies. Personnel cannot be brought. The system will provide an assistant."
"Who is the assistant?"
If there was an assistant, Haizaki naturally hoped they would be reliable.
Even with memories from his previous life, at his core, he was still just a man with extra apocalyptic memories, greater courage in the face of disaster, and a willingness to sacrifice—a normal person.
Just a normal person—no superpowers, no exceptional skills.
"The following list contains eligible assistants."
Haizaki scanned the list quickly and noticed a common trait.
"Why are they all female?"
"Only males and females together can ensure the continuation of humanity. When the system user is male, the assistant must be female."
"Can I designate the assistant?"
"Currently, the assistant is randomly selected by the system."
"Will the assistant know about the system and the mission?"
"The system will not inform the assistant of any information regarding the system or the mission."
"If both of us die in the mission world, what happens? If one dies and the other survives?"
"Death."
"After the mission ends, what happens to the two of us?"
"The system user will be unaffected. The assistant will retain no memories of the apocalyptic world."
"If both the assistant and I survive until the end, is there a hidden reward?"
"Please explore on your own."
"I see…"
Haizaki continued asking many more questions.
...
Ten kilograms of supplies was not much. Even if entirely filled with food and water, it would not last long.
Thus, Haizaki rushed to a supermarket and purchased a small amount of compressed biscuits and chocolate, along with condoms.
Afterward, he went to a pharmacy and a military surplus store to buy medical bandages, high-proof liquor, antibiotics, a utility knife, a magnesium fire starter, and a compass—common survival items.
Using the internet, Haizaki downloaded electronic materials related to wilderness survival, machinery, electricity, animals, and plants onto his phone.
Two mobile phones. Two solar power banks.
That was everything Haizaki prepared for the world of the "Solitary Apocalypse."
However, before officially entering the apocalypse, there was one more thing he absolutely had to do.
Schedule emails to be sent to his country and to governments around the world. In the end, he could not guarantee that he would successfully complete the mission and return alive.
"I am a time traveler from an apocalypse three years in the future. Please do not take this as a joke. I am serious."
"Today is July 1st, 2019. Below are major events that will occur in the future. Please read the full text before carefully judging the authenticity of this message…"
"July 18th, 2019. A fire breaks out at Kyoto Animation's 'Studio 1' in Japan…"
"August 18th, 2019. Eastern Union…"
...
"October 12th, 2019. Typhoon No. 19, 'Hagibis,' makes landfall in Japan. On the same day, Sakurajima Volcano in Kyushu erupts, a powerful tornado appears in the Chiba region, and mountain floods occur in Kanagawa…"
"November 9th, 2019. New York, United States…"
"January 25th, 2020. Paris, France…"
...
...
"March 21st, 2021. Apocalypse phenomenon code name [Revenant Resurrection]. Viral entities known as 'Revenants' appear. Their emergence locations, physical characteristics, attack methods, and handling procedures are as follows…"
"May 18th, 2021. Apocalypse phenomenon code name [Collapse Beast Rampage]. Silicon-based lifeforms known as 'Collapse Beasts' appear. Their emergence locations, physical characteristics, attack methods, and handling procedures are as follows…"
...
"September 29th, 2021. Apocalypse phenomenon code name [Ironblood Machine Tide]. Mechanical lifeforms known as 'Ironblood' appear. Their emergence locations, physical characteristics, attack methods, and handling procedures are as follows…"
...
"January 1st, 2022. Apocalypse phenomenon code name [Azure Deep Sea]. Unknown marine lifeforms known as 'Deep Sea' appear. Their emergence locations, physical characteristics, attack methods, and handling procedures are as follows…"
...
"February 18th, 2022. Apocalypse phenomenon code name [Originium Catastrophe]. Unknown demi-human entities known as 'Infected' appear. Their emergence locations, physical characteristics, attack methods, and handling procedures are as follows…"
...
"March 23rd, 2022. The United Human Government announces the 'Ark Project,' beginning strategic evacuation. Humanity abandons the home it inhabited for three million years."
Hopefully, in this life, the apocalypse will never come.
Humanity will prevail!
—A normal person who personally witnessed the fall of human civilization.
...
Haizaki recorded all the apocalyptic intelligence from his memories in the most concise words possible—information bought with countless lives and rivers of blood, including outbreak times, locations, crisis types, and effective human countermeasures.
If there had been more time, he would have liked to include images of the disaster creatures to help nations prepare more effectively. The golden-haired twin-tailed tsundere girl he knew in his previous life would have been the perfect candidate—her drawing skills aside, the most important reasons were confidentiality and trustworthiness.
But there was no time now.
Considering the issue of international trust, Haizaki attached a long list of names and additional intelligence. These were materials he had obtained from the United Human Government during the apocalypse. For present-day nations, these lists and documents held immense value—they were all classified information.
After finishing the emails and adding all recipients, Haizaki leaned back in his chair and let out a long breath.
With this information, even if countries only chose to believe it a single day before the apocalypse, humanity could still significantly reduce its losses.
The outbreak date of the "Disaster Apocalypse" was March 21st, 2021. The scheduled send time for the Eastern Union was July 1st, 2019, while emails to other countries were delayed until December 1st, 2019.
He wanted his homeland to have more preparation time. His country needed to protect a population that made up one-fifth of the world. This was the only advantage Haizaki, as a member of the Eastern Union, could leave behind.
The recipient addresses were all secret government emails he had memorized in his previous life, ensuring the messages would reach individuals with sufficient authority.
The greatest advantage of a time traveler was information.
Haizaki also prepared another version of the email, scheduled to be sent on December 31st, 2020, addressed to people he had been familiar with in his previous life.
At the very least, it would increase their chances of survival.
"I've done everything I can. What comes next, I'll face alone."
Facing an unknown apocalyptic world, he couldn't help feeling nervous—but also curious and expectant.
What kind of world was the "Solitary Apocalypse"?
Was it the same type as the Disaster Apocalypse he had experienced?
And who would the system randomly choose as his assistant?
"'Solitary Apocalypse' initiation confirmed. The system user will enter the 'Solitary Apocalypse' world in ten seconds. Please prepare."
The auxiliary spirit's voice was mechanical and emotionless.
"Ten."
...
...
"One."
"Commencing entry."
Haizaki's vision blurred, and his consciousness gradually faded away.
...