His own disguise was simple. By writing in his book, he could change reality. As long as it didn’t affect others, he could successfully use it to hide his true nature.

-Volume 4 page 74

In a short time he would be shot to death by Kiyoko Takekura. That was the future Yukimasa Aihara had just read about. The small paperback book he possessed told him about the near future. And even though he knew it was coming, now that it was already written down, there was no way for him to change it. If things proceeded as planned, unable to resist destiny, he would be forced to do exactly what the book said.

“Let’s erase as much as we can, then.”

However, Yukimasa could rewrite the contents of the book. And in doing so, he could control his own actions and the events happening around him.

Tracing the letters on the page with a finger, he watched them disappear. He could only erase from the part of the text that occurred after he had climbed up to the ceiling. After all, he had taken up his position there just a few moments before, and he couldn’t change things that had already occurred.

Yukimasa considered what developments should follow. By writing in the book, he could alter the future, but he couldn’t simply write anything that came to mind. He could only put down things that seemed plausible, and he couldn’t do anything that contradicted earlier parts of the text.

So, how would he proceed? It seemed that Kiyoko knew Yukimasa was here. She was probably coming here specifically to kill him, so it would be hard to change such a firmly rooted action. Just in case, he tried writing that Kiyoko wouldn’t enter the room, but the letters vanished immediately. Her arrival was already set in stone, so he would need to change something that didn’t directly involve her.

Yukimasa flipped through the book, looking for something that might be useful in this situation. The first thing he thought of was bringing another classmate in to fight her. Luckily, it looked like a number of other students were hiding inside the wall nearby.

Kiyoko enters the room. At the same time, another person enters from the opposite door. He wrote the words quickly and waited for a short while. The letters didn’t disappear; the rewrite had been accepted.

-Volume 4 pages 119 and 120