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Senku believed in parallel universes. Even though there was technically no concrete evidence to prove their existence, it was one of the few theories he wholeheartedly believed in without needing said evidence.
As a child, parallel universes were not something that he thought about often. Science that was more on the abstract side, something that could not be proven so easily, was science he did not actively put any energy in. At that age, Senku had much preferred to learn about proven science, about how the world around him was structured. He much preferred experimenting with different chemicals or learning from Dr. X.
Then he got older. Things changed. Senku’s favourite thing about science was seeing how the world worked, including how the whole universe functioned. Sometimes, certain elements in science simply did not have enough evidence to turn them into a proven theorem or they had just a tad too many loopholes to them. Senku understood that and embraced that.
One theory which he did not believe in at all however was the multiverse theory. The parallel universes theory. Alternate universes. He could understand the logic why people might believe that other universes out there existed, but it didn’t resonate with him. There were just too many variables to consider; did the action of one person determine when the universe branched off or was it the actions of multiple people? Can every single person affect the branching of parallel universes? How would there be enough energy to sustain that split? Would it have taken years for the alternate universes to form or would it take a matter of minutes? Did people’s decisions really affect how universes split or was it something else? Could a parallel universe start to exist due to a sudden elemental reaction or due to a new blackhole emerging? Or was it something else entirely, something that the mind of the human species would not be able to comprehend?
Alternate universes just had too many variable, too many loopholes, would break too many laws.
And then, everyone turned to stone. After thousands of years, Senku broke free. His friends broke free. He made new friends. He went through hell and back establishing the Kingdom of Science. Everyone had placed their trust in him during their stay at Treasure Island, where they found truth after truth.
On the Perseus, Senku laid awake, alone and lost in thought.
…Byakuya…
The last time Senku had seen Byakuya was thousands of years ago, before the Medusa turned everyone to stone. Byakuya had escaped it, alongside the other astronauts. Underneath them, the whole world had been turned to stone. Whilst Byakuya was still alive, Senku had been trapped in stone, counting each second. Byakuya didn’t know where Senku was. He never knew what happened to Senku’s stone body.
It was only a matter of time before Byakuya passed away.
When Senku had broken free, Byakuya had already died.
Senku had never said a proper goodbye to Byakuya.
To his dad.
Senku missed him. From all the people that Senku wanted to see the most, it was his dad. To see him, to hug him, to laugh with him.
Senku couldn’t help but let his mind wonder in the lonliness of the night…
Was there an alternate universe out there where Senku got to say goodbye to Byakuya? Was there, potentially, an alternate universe where the two of them would have been together? Petrified together? Or was there an alternate universe where the Medusa didn’t exist, where it didn’t petrify the world? Where they could have had a normal life, where Byakuya could have seen Senku grow older?
If parallel universes were indeed real…
Then why was Senku born in this universe? Why was he born in the one universe where Byakuya didn’t live anymore, but only lived in Senku’s memories?
As much as it upset Senku that he had to live in the universe where his dad had died before he could even say goodbye, another part of him felt comforted by the idea that somewhere out there, in an alternate universe…
The two of them were together.
Senku believed in alternate universes. Whether or not they were real, it didn’t actually matter. No, Senku just wanted to look at the stars and believe that somewhere out there, he was with Byakuya.