What makes a good "Chosen One"?

Ichimaru won the war.
But the victory felt empty in his hands as his remaining allies left him behind. There was no family, no friends, waiting for him to come home. There was only the pain of a broken soul and a body that was quickly dying, so when Keisuke offered him another chance, he took it with open hands.
This time, they would stop Bonnet before the man destroyed everything they loved.