My adventure in a fantasy world

The story follows two brothers, Cain and Rei, who had been living their lives peacefully..... until on that fateful day, that happened, Strange people from another world descended upon earth, announcing some prophecy and the birth of a hero. To Cain's surprise who witnessed it all first hand, there came a light from his house two days later while he was out to find more clues on the strange people who came on earth, the hero, the younger brother seemed to have been chosen as the one which they had announced about, "Rei you- you are the prophecies hero ?" A life changing moment took place in Cain's eyes, he has been given two options, to stay with his parents at earth or go along with his brother to another world and fight as a warrior beside him to defeat the demon king and bring peace to their world. But surely, every action comes with a consequence which decides your own fate, in Cain's case, it was in a form of karma....a betrayal.