The Sword Emperor Transmigrates - Chapter 157

However, he did not know that he was not raising just a harmless pet, but a biological weapon secretly made by the government… a real monster.

As a former librarian, Rand felt that he had been living an ordinary life, the one that he had reclaimed unconsciously every single day.

Recently, he has been a little upset because the pet fish he accidently brought home to raised seems to have undergo some strange changes

Well, it turned into a merman.

- Description from Novelupdates

[No fixed CP + wear books + brain hole cool text + women disguised as men + group pet]

Gu Lan crossed over and became the cannon fodder of the original book disguised as a man, counterattacked the protagonist of the original book who slapped her face, and lived in a dormitory full of sickly beauties.

Until one day, she discovered that her roommates were villains from other horror novels. After discovering the secret, Gu Lan thought she would be killed, but her roommates all looked at her strangely… Contrasted with cute Zhengtai, sickly and beautiful boy, split personality school girl, cold and stern school bully, romantic and noble son who plays Shura every day field.

- Description from novelbuddy

Ye Chen, once the unrivaled immortal standing at the pinnacle of the cultivation world, fell at the final hurdle—his last heavenly tribulation. Struck down by the wrath of the heavens, his body was destroyed, his cultivation shattered. Yet, instead of vanishing into oblivion, his soul defied fate itself.When he opened his eyes again, he was no longer in the vast cultivation realms but in the familiar yet distant world of modern Earth—inside the body of his younger self during his high school days. Armed with the knowledge and power of an immortal, he would rise once more, overturn destiny, and reclaim his supremacy in this new world.

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.....

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