Suko got bored while walking around with the author, took out his phone, and started writing a story to himself. In that instant, he stepped outside reality and was able to observe all universes beyond the one we live in. Everything outside our universe, from universes to tanriverses, was erased.
Then Suko bent Absolute Reality and rewrote the code of the universe we live in. He rewrote its ending. Not a single universe or tanriverse remained. Only our universe was left.
After that, Suko returned to the author's world. He erased the Sun, all planets, asteroids, and moons. Only Earth remained. Light existed without a Sun, darkness fell without a Moon. No one noticed any of it, because Suko altered reality itself and created an illusion.
He rebuilt the system of the world entirely. Evil no longer existed, everyone was good. The distinction between ugly and beautiful disappeared. Everyone became beautiful and handsome. Everything adjusted the moment he thought of it. Evening came, but no one noticed, because he bent everyone's mind into believing it was evening. Darkness fell without a Moon, the Earth stopped rotating, yet people continued living inside their own reality, unaware of morning or night.
Suko thought of all these changes within 0.000000000001 Planck seconds, rewriting every line of code one by one. When everything was complete, he finished the novel.