Kokushibo was finally killed, the demon slayers finally succeded in that task, and with no longer any remaining demon moon in their path, they left the remainings of the second most powerfull demon to his demise.
Meanwhile, Kokushibo was wondering at what point of his life It went downhill, when he started hating his twin brother so much. He wishes he did things different.
He wants and begs whoever god there is to give him a second chance.
One hears his prayers, and takes pity of his broken soul, granting him the sencond chance he is asking for....
In an alternate universe where things are slightly different.