Reborn as the Harem King - Chapter 1 Rebirth

Riding out the apocalypse on a tropical island isn't exactly a vacation. When mana arrives on Earth, Coop finds himself isolated in paradise with only one real option to survive. He needs to claim a civilization shard and level up. Coop maximizes his chances by carefully selecting a class and committing to progression. He’ll need to grind thousands of monsters to compete on the system's leaderboards while upgrading his settlement to represent the factionless.

Ruins stretched across the landscape in the apocalypse after the nuclear war.

Well-known Composer Fang Zhao was in the glorious stage of his career, when the Apocalypse arrived; After finally experiencing the bitter difficulties of a thousand dangers, when the Apocalypse was simmering down to an end, he collapsed; When he opened his eyes, he was reborn in a New World, 500 years after the end of the apocalypse, in the body of a student who had been dumped barely after graduation, who had been cheated of his hardwork barely after he started working…

The World of the Future, Virtual Idols PK Real Idols

“Every time background music plays in my head, I feel like there is nothing to be afraid of.” —Fang Zhao

Toward the end of the apocalyptic period, Fang Zhao lost his life. However, instead of dying, he found himself 500 years later in the body of a young and aspiring composer who shared the same name. Having received a second chance at life, Fang Zhao sets out to achieve the previous owner’s dreams.

Armed with the experience of living through an apocalyptic age and his profession as a composer before that period, Fang Zhao uses his talent, wits, and knowledge to make his mark in the entertainment industry of the future.

- Description from Novelupdates

Transmigrating into a poor and mistreated young lady's body, what will the craziest alchemist of the seven realms now do?