I am back, But as a divine hunter

After some of his comrades died, The hero Jetrin take an oath to change the world and to kill the demon lord Cain, but after a long journey they finally meet the demon lord and fight with him along with his comrades. The hero Jetrin was so angry and defeated the demon lord Cain, but when he finally think that's the end, He was betrayed by his comrades and stabbed him through his heart using his Holy sword and died with a smile. His comrades was confuse because The hero Jetrin died smiling, but one thing that they didn't know is that someone with an unknown existent helped him and offered him something but in exchange his memories. [Don't worry for I will give it to you in the right time and the right place] The hero Jetrin take a gumble and accepted his offer, Later he found himself living his life to the Earth but sadly he died again. The hero Jetrin meet the Unknown existent again and finally made a contract with him by exchanging his memories to the earth and by giving his class as a hero. "I finally back! but...wait! as a divine hunter?" And that's the start of his journey as a revenger and as a divine hunter.