World of Warcraft: Conquest of Arthas - Chapter 25: WOW : Ferment Your Body

A man who was once called the world’s strongest agent ended up becoming a teacher after his retirement, to train a new generation of agents. After many years of training his disciples, he was killed at the age of 60 by a secret organization’s ruse and was reincarnated in another world with his memories intact. Though he was surprised by the existence of magic and the strange species in that world, he quickly adapted to his condition as a newborn and took advantage of it. He acquired special magic and gained a massive amount of strength thanks to his rigorous discipline, in order to reach his goal: Resume his career as a teacher which he left halfway through in his previous life. This is the story of a man, who, based on the memories and the experiences of his previous life, became a teacher who travels through the world with his students.

“Han… Yi Jin? The dual-class loser villain bastard, Han Yi Jin?”Han Yi Jin had reincarnated as an insignificant villain in a male-oriented modern fantasy novel.Han Yi Jin, the small-fry villain who hung around the main character, Kang Yoo Hyun, and died at the beginning of the story.“Aren’t you acting a little strange today?”“What’s strange? F*ck off if you don’t have any business with me.”To avoid suspicion, he acts like Han Yi Jin from the original story. This rather attracts the attention of the gongs, and Yi Jin is looked upon with suspicion.[Synchronisation is complete.] Shake the Catnip (S): All stats of the designated opponent +20%In the meantime, he had acquired the “Catnip Skill” from nowhere.Because of this skill, which becomes more effective the higher the intensity of the skinship, Yi Jin begins to attract the obsession and interest of the other characters…“I love it when you curse.”“Hyung, would you like to go out on a date with me?”“You wouldn’t think of that if I cut off at least one of your legs.”“Keep running away like that. I’m curious how far you can go.”These crazy bastards are obsessed with me.“Why are you all staring at me with those eyes? Get the f*ck out of here, you crazy bastards!”Will Yi Jin be able to escape safely from the clutches of the gongs?Will he be able to escape death?

Demons, devils, ghosts and monsters

Plunge the mortals weak in horrors;

Arms of gods and blades of devils,

Shroud the world in untold evils.

Lu Sheng was an ordinary civil servant in the modern world. After waking from a drunken stupor one day, he found himself trapped in a dangerous world where demons, ghosts and supernatural monsters terrorize the land.

In this world, ordinary mortals live in dark fear and helplessness, without any means to fight against the supernatural.

As Lu Sheng struggles desperately for survival, he stumbles upon a game mod he had designed for a mobile phone app in his previous life. It unexpectedly becomes his special ability, which enables him to instantly level up any skill he learns, albeit at a cost.

Thus, Lu Sheng begins his journey, striving for power beyond the reach of a mortal as he treads the way of the Devil…

- Description from Novelupdates

Another entry in what you can call the Proto Harem Series: the books written before the Harem Series that take place in the same world.

It’s about a swordswoman whose student is captured, so she goes to rescue her.