It wasn't like Hojo had left clear instructions on how to reverse a sacrifice to the Gate.

From the beginning, there was something odd about Namimori. In a world where every city had its own method of dealing with the bane of humanity that were ghouls, Namimori was the first place Reborn had ever been that felt safe to him. People were calm and unafraid on the streets, even after dark. It was remarkable and at first he thought it was due to the fact that Namimori's police force had some sort of foolproof guard against ghouls. But then he noticed the distinct lack of graveyards. By the time Reborn really understood what kept Namimori safe, it was too late to do anything about it. After all, the successor was being tutored, the guardians were chosen, and Xanxus was bearing down on them with half the Vongola rings and all of his wrath. All there was left to do was wait and see.