Killer J's feed

Can someone explain to me the chapter 1 and 2. I DIDN'T UNDERSTAND IT. DID HE TRAIN WITH THE HEROES FOR THOUSAND OF YEARS AND DIED AND THEN REINCARNATED WITH A WEAK BODY? OR WAS HE BORN IN A WEAK BODY THEN GET HIT BY A BOW HAD A COMA FOR 6 YEARS WHILE IN COMA HIS SOUL GET REINCARNATED TRAINED BY THE HEROES OF HE WAS TRAINED HE RETURNED TO HIS BODY? IS THAT IT?