"Dr. Stone Reboot: Byakuya" is a spin-off manga that serves as a prequel to the main "Dr. Stone" series, focusing on the events surrounding Byakuya Ishigami and the other astronauts who were in space when humanity was petrified. The story begins with Byakuya and his crew aboard the International Space Station (ISS) as they witness the mysterious green light that turns all life on Earth into stone. Stranded in orbit, they must grapple with the sudden isolation and the realization that they may be the last unpetrified humans alive.

The narrative delves into the astronauts' efforts to survive and maintain hope while cut off from Earth. Byakuya, a former engineer and the adoptive father of Senku Ishigami, emerges as a central figure, driven by a determination to return to Earth and find a way to reverse the petrification. The crew faces numerous challenges, including limited resources, the psychological toll of their situation, and the need to devise a plan to safely re-enter Earth's atmosphere without proper support from ground control.

As the story progresses, the astronauts work together to develop a strategy for survival. They use their scientific knowledge and ingenuity to create tools and systems that will allow them to endure their extended stay in space. The manga highlights their camaraderie and resilience, as well as the emotional weight of their mission. Byakuya's leadership and unwavering optimism play a crucial role in keeping the group united and focused on their goal.

The narrative also explores the astronauts' eventual return to Earth, where they discover the petrified world and the absence of any signs of life. Despite the bleak circumstances, Byakuya and his crew remain committed to their mission, laying the groundwork for future generations by preserving knowledge and resources. Their actions set the stage for the events of the main "Dr. Stone" series, as their efforts ensure that humanity has a chance to rebuild civilization.

The manga provides a deeper understanding of Byakuya's character, his relationship with Senku, and the sacrifices made by the astronauts to ensure humanity's survival. It complements the main series by offering a detailed account of the events that occurred during the petrification and the immediate aftermath, enriching the overall narrative of "Dr. Stone."