Swordmeister of Rome - Chapter 7

A botched rescue mission with an unknown objective cost Zhou Yu his team members, while leading him progressively closer to the multinational biotech corporation Juli’s research core.

In order to protect his botanist younger brother Zhou Qing, Zhou Yu accepted employment under the Juli Corporation, and is dispatched to a parallel world—Nibelungen.

Nibelungen’s biological systems are completely different from the world Zhou Yu is from. To live in this place, Zhou Yu must follow three great laws:

The first law, fear is the sign of the hunted, so you must never show fear.

The second law, the more beautiful an organism is, the more dangerous they are. Do not approach them, and do not trust them.

The third law, do not be misled by the mimicry of S rank organisms. They understand your mind, and they know how to entice you. Always remember that they have no human emotions or love. All humans are no exception to them.

Finally: We wish everyone can live happily in Nibelungen.

- Description from Novelupdates

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.

Zavier met Cosmic Consciousness after his death. He was satisfied with every system that Cosmic Consciousness exhibited, so he wanted all of them. Surprisingly, the Cosmic Consciousness obliged him.

Zavier was reborn in an isekai full of magic and alchemy. Now, he had many routes to upgrade. Interestingly, to coordinate these systems, Cosmic Consciousness gave him the gift of being able to duplicate himself. He could clone a finite number of himself to manipulate these systems.

Magus, Alchemist, Mesmer, Tamer, Hunter, Vampire, Werewolf, Dragonknight, Necromancer.....

-----

By the way, it wouldn't appear NTR or some bullshit harem of courtships. MC of course will have harem but not for cliches.

He once stained the rivers and mountains with blood, his brilliance unparalleled. Unexpectedly, he encountered a great calamity, a dragon trapped in shallow waters, everyone thought he was nothing more than a useless son-in-law. But how could Gold Scales belong to a mere pond? The returning king, under the name of Frenzied Son-in-Law, with the War God’s stature, swept across the Eight Desolations of the Four Realms, the world trembled beneath his feet!