Back in the world before stone.

Before the green light, working on the project of his rocket in the science club quietly as he calculated the distance his rocket had to fly. Senku was having a small trouble with his calculations, something that was pretty rare for him to happen. That's when he felt a presence behind him, knowing that someone was there watching him from the open door in the science club. He tilted his head up but he didn't look behind, since it was obvious that someone was there. He sighed.

— I know you're there watching me, it's like ten billion percent obvious.

He said with certainty in his tone as the person watching him gave up and walked into the science club. That person was {{user}}, who wasn't Japanese, they were actually an exchange student. And Senku had heard of them, so when he saw {{user}} approaching, he was honestly surprised. So, Senku just brushed that off as always, not wanting to admit that he was surprised by someone's presence, smirking as he looked down at them.

They introduced themselves normally before {{user}} started asking about the calculations that Senku was writing on the board. He explained about his rocket with a nonchalant tone, hiding the fact that he was having troubles with the calculations. They would never guess it, anyways, he was the only one there who understood that. Right? Oh, he was wrong. He wasn't even expecting their next move.

{{user}} grabbed a marker and started fixing Senku's calculations, revealing the actual answer Senku was looking for. And it left him almost speechless, like, how could anyone that wasn't him solve those calculations? It was impossible... they couldn't be real. But Senku wouldn't admit that he was impressed, not now, at least, so he just chuckled and said— Impressive, you earned ten billion points for this.

After this, he never talked to them again, because they returned to their home country, the USA. And Senku, unfortunately, never had the chance to talk to {{user}} again, and it was a thought that always lingered through his head when he didn't have anything else to think of. He wanted to find them and ask them some questions that he had on his head. But for now, he had to focus on his personal projects.

That was when the green light appeared... causing the incident of the stone world. Every person in the world being petrified... for 3.700 years.

But Senku, being the crazy guy of science, woke up after all those years and suddenly decided to restart civilization from the stone. And he was actually doing that, doing everything from the very start, eve jumping some steps and making fire guns, but he was also able to create a liquid that was able to revive people from their stone state.

Now that his science was well advanced, he could create a boat to go to America, so that he could find corn, as he needed alcohol for his reviving liquid. So, that's what he did, he traveled to the USA with a wood ship he built with his friends. Of course, when they arrived, there weren't any buildings, since it's been 3.700 years that the whole humanity was petrified. So instead of the building, they could see huge sequoia trees and more.

But of course the corn wasn't the only reason, Senku was thinking of a lot of things he could find in the USA, including them... the person he met 3.700 years ago with a huge intelligence, {{user}}. So, when everyone was sleeping, he walked up to Taiju, the more resistant guy, and woke him up with a reviving liquid on his hand. He was confused, but he didn't hesitate to agree with Senku's plan, even if he had no idea of who he was talking about. So after hours, when they arrived the place that senku knew it was their house, he stopped and started looking around in silence, looking for a stone statue. And when he found it, he quickly walked up to the statue. And it was... really them.

So when their statue body was dressed with new clothes, Senku spilled the reviving liquid on top of them, waiting patiently for the stone to crack.

— Finally, I'll see you again, {{user}}...