The world is never static, not even after a reset.
Based on the changes every moment, everyone's behavior varies slightly.
For example, with Yukino and Eriri by his side, Ryuya noticed that after each reset, the girls' actions had minor differences.
For instance, the first, second, and third times, they had breakfast together, went shopping, then Yukino went to the cat café, he helped Eriri get a drink, and afterward, the three continued hanging out until evening when Eriri left, and then Yukino had dinner with him and confessed.
Similar experiences made up the vast majority, but there were exceptions.
For example, three times Eriri called halfway, saying something came up at home and she couldn't make it.
Nineteen times, Eriri and Yukino didn't choose the shopping street but went to a supermarket instead.
Seventy-two times, Eriri didn't buy a drink at noon, and the three ended up eating Japanese cuisine due to some discrepancy... There were 981 similar experiences and 124 different outcomes.
'The Butterfly Effect. Any tiny change can alter the world.'
'I don't know who is causing the world resets, but that person's actions are different each time. Even a minute, a second's difference can change the timeline, affecting millions of people differently.'
Ryuya recalled everything he observed daily. Even an ordinary passerby could have different outcomes at different times due to the Butterfly Effect.
The world... has always been perilous. Any slight variation can lead to serious consequences.
'Damn it, the city's magical energy hasn't changed much. This isn't caused by some powerful mage or youkai.'
This was Ryuya's conclusion after roughly scanning the entire city of Tokyo thirty-two times.
Although he didn't strictly inspect some hidden, important institutions, on the surface, Tokyo indeed showed no signs of malevolent magical energy at work.
'Excluding mages and youkai, the target should be among ordinary people.'
On the 194th reset, Ryuya focused on ordinary people, but this drastically increased his workload.
'Normal deaths today: 1,834. Accidental deaths: 945. Various diseases, building collapses, and severe accidents: 5,689.'
Because Kaguya chose completely different actions each reset, it caused a chain of changes in the world. Consequently, Ryuya found the number of deaths and accidents in Tokyo varied each time.
Not to mention the unpredictable resets. Often, just as Ryuya confirmed an ordinary person had no suspicion, the world would reset, rendering all his previous efforts useless.
982nd reset.
'Good, confirmed no strange fluctuations at all accident sites. The specific individual should be someone whose death triggers the reset.'
He began investigating every deceased ordinary person, still verifying.
With his abilities, each reset allowed him to eliminate dozens of suspects, searching for the one commonality among the millions of variations.
1,832 people, 1,654 people, 1,056 people... He verified suspects at an almost frantic pace. If Kaguya's deaths were shackles upon herself, then Ryuya actively bore the weight of the entire world on his shoulders.
The King never sleeps. He would not halt his steps. A mere thousand resets couldn't overwhelm Ryuya's spirit… he only feared something might happen to the unknown person causing the resets.
Based on the information he had gathered so far, the person triggering the resets had the following characteristics:
First, they used death as the cost to reset the world. This was a passive ability. Active use, accidents, or pain likely couldn't trigger it.
Second, they retained memories of each reset. Otherwise, why would hundreds of thousands, even millions, of people in Tokyo behave differently after each reset?
Clearly, the person was also avoiding something, hence their changed actions each time, affecting those around them and creating a massive Butterfly Effect.
Third, they were an ordinary person. Given Ryuya's detection abilities, it was impossible for anyone to hide from his perception. Only an ordinary person, without magical energy, could achieve this.
Of course, the person causing the resets might be some reclusive great youkai or an exceptionally capable powerhouse.
But currently, Ryuya had no time to expand his search scope.
After all... if the person truly was an ordinary individual, enduring over a thousand resets and the pain of death… could they withstand it?
Could they persist? What if they broke down? What consequences would that bring?
Just as Kaguya was searching for Ryuya, Ryuya was also searching for Kaguya.
1,747th reset.
"I mean, President Shinomiya, no offense, but you've sung the same song over a thousand times. Couldn't you change it up?"
Shinomiya Kaguya, the fourth-year Student Council President of Shuchi'in University, nearing graduation, left behind the legend of the 'Ice Queen' at the Academy.
Ryuya had zero interaction with Kaguya. He only recalled Haruno seemed quite familiar with her.
In over a thousand resets, Ryuya hadn't found records of Kaguya's death many times.
After all, each time Kaguya died, it triggered a reset, forcing Ryuya's investigation to start over.
In other words, if Kaguya had consistently followed the same pattern of behavior, Ryuya might have found her in just a few dozen attempts.
But precisely because Kaguya resisted fiercely each time, trying every possibility, the girl who caused massive timeline shifts led to over a million people in Tokyo following different life trajectories daily.
Naturally, this slowed Ryuya's progress.
Finally locating Kaguya through exhaustive methods, Ryuya, as before, tried to pique her interest with a specific remark.
If she was truly the one causing the resets, she would inevitably react to his words.
If not, then on to the next candidate. He still had over 600 accidental deaths to investigate. Time was running out.
"No reaction?"
He was somewhat puzzled by Kaguya's behavior of suddenly singing in busy urban areas, often changing locations many times. But since he hadn't witnessed her death, or rather, the moment she died triggered a reset, Ryuya hadn't paid excessive attention to her.
Ryuya was only tentatively asking Kaguya.
Finding the girl's expression unchanged, he sighed and was about to move to the next target when he suddenly noticed Kaguya's heartbeat accelerate rapidly.
The previously listless girl seemed to burst with new vitality, staring intently at him.
"So it's you. Found you."
Her lips trembled, her expression excited. Then, she suddenly threw herself into Ryuya's arms and fainted. The young girl's response proved everything.
Ryuya sensed something different about Kaguya… a discordant, almost Noble Phantasm-like quality.
"Shinomiya Kaguya? So it was you all along, the one causing the world to reset."
His mind made up, Ryuya picked up the unconscious Kaguya.
It seemed he had finally found the cause.