The Starting System Is Added, but Ironman Mode

A time traveler, selected by the system, can freely travel back and forth between modern times and half a century ago. The system gave him almost the power of a creator god, but it also gave him the responsibility for the rise and fall of the world. In that familiar yet unfamiliar parallel world, he found that he was being held up. He had to make progress even if he didn't want to, and it was not up to him.