Apocalypse: I Build A Doomsday Train - Chapter 458 - 273: Supreme Doctrine

Before going to college, an ordinary high school student went to celebrate and got drunk. When he woke up, he found himself in a completely different world. There was a big sect, the approaching sect entrance examination, a slum where his body’s previous owner lived, and a shared memory about a missing young girl.

When he got tangled in a fight with a few punks in this different world, he fell off a cliff and miraculously found himself still alive, with two more voices ringing inside his head. They were Sword Master and Saber Master. In the company of them, he continued to find out more about this whole new world. He took the sect entrance examination, entered the sect, met a strange man in black, and even participated in a major competition of the sect to have a chance to win over his peers!
In this whole new world, he was born again and got to explore the fantastic martial world!

- Description from Novelupdates

(Warning Mature Content R-18)After a catastrophic plane crash, a group of college students find themselves marooned on a mysterious, uncharted island teeming with an ancient, aphrodisiacal energy. As they adapt to their new reality, the island's seductive influence heightens their libidos, awakening latent powers alongside primal urges of lust, envy, and avarice.Beneath the paradise-like facade, the island proves to be a manipulative prison, thriving on their deepest desires and fears. Survival hinges on more than just overcoming the island's perils; it demands they confront the beasts within, where every alliance is tested by temptation, and every passion could lead to their ultimate downfall.

Betrayed and left for dead, Richard Blackwood—formerly known as the world renowned hero Astralis—awakens a decade later to find the world has moved on, and an imposter now wears his mantle. Disguised as a rookie in the Mage Guild, he quietly hunts for answers.'If my little sister is levelled above me, then what about everyone else? How much stronger have the bastards who betrayed me grown while I was dead?'Richard must grow stronger once again, and rise much higher than the S-Rank.'What the fuck? I almost die, and I get a power up?'Not harem.