A World of Terror, Revenge on Reincarnation

The world in which 24-year old warrior, Aziel lives and fights in is coming to an end. Humanity has been obliterated, and he gets a 'one-in-a-billion' chance to get reincarnated and isekai'd into another world, where he'd have the same objective; to defeat the multiversal organisms called "Demons", and secure all other dimensions from them. However, there comes in disturbance from other sources as well, leading to his close calls with death, yet powering up exponentially and consistently improving over time. A meet with an old lover; a coincidence or fate, even if unknown stirs something in him, leading to a series of events. Will the reincarnation of Aziel be ever successful in achieving his goal? It's all a matter of patient waiting and guessing :)