Kuroi Ashiro, age 21, has died 4 times, returned and regressed 4 times each. This is his final isekai, and last life.
In his original world, looms a devastating first apocalypse signalling the sign of the end of all worlds, Cosmic Beasts, Mutated Beasts and Dungeon gates and other worlds are invading, all infected by Greed for the first universe or the fall of their own.
Ashiro remembers everything he did in his past lives after he dies, and the time he has in the isekai world depends how long it takes to be destroyed by its first apocalypse.
He was as a Expert Mecha Engineer and Scientist in his first isekai fighting againt cosmic beasts for over 43 years in a Sci-fi world, returned after Human Federation collapsed to a cosmic beast hive mind and the Insectoid Alien Species broke through the defence lines.
Died 2 years after returning to his original world after the first apocalypse. Fail.
In Ashiro's second life regression, his isekai world was a fantasy world, where Humans are fighting dungeon breaks, Ashiro became one the best battlemages and one of the greatest arcane blacksmiths, returned after 20 Years when all 163 dungeons broke loose and the 7 liches were released.
Died 4 years subsequently from assassination after returning to his original world. Fail.
In Ashiro's third life regression, his isekai world was a martial arts world, where the strong rule over the weak, with no technology nor reliable laws, embracing this Ashiro became a Grandmaster Martial Artist after 53 Years in 5 different martial styles, returned consequently from world after it being overrun by mutated beasts.
Died 1 year after the first apocalypse from betrayal. Fail.
In Ashiro's fourth life regression, this isekai world was a planet similar to his first universe but, the newly formed 13th universe, is the first to fall to the apocalypses, and the last dimension left in 13th universe, Planet Azure.
A modern technology advanced world being invaded by the fallen worlds and voidbeasts from the rest of the 13th universe, ushering the Primevil Age of the last galaxy in the 13th universe.
Ashiro created a Hunters Union using his knowledge and created martial halls and magic towers as well as advancing the current mech and battleship weapons technology, fighting dearly for survival Humanity struggled together and finally collapsed after 13 years.
Universe 13 Swallowed by the Prime Evil singular entity. Fail.
Ashiro calls this Prime Evil, Nemesis. Devourer of Worlds. Harbinger of the End.
Now it's Ashiro's Fifth, and last life from his unique ability.
[X rank - Regression V Returnee]
[Abilities - SoulBound Memories, rewind]
[Limits - Isekai 5 times, Regress 4 times]