One Piece: Capitalist Brook's Crew Expansion Plan - Chapter 46: The Thunder God’s Altar – Rumble-Rumble Fruit

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.

Zhang Ruo Chen was the sole male heir of one of the nine emperors of the Kunlun Field. Ruo Chen’s father was known to all as the “Enlightened Emperor”, however Ruo Chen didn’t just leech off his status as emperor’s son. He proved himself to be a dragon amongst men, possessing a heaven defying body, and managing to cultivate to Greater Perfection within the Yellow Horizon Realm, at just the young age of 16.

But even though he stood at the summit of the younger generation and had a boundless future, he sadly died at the treacherous hands of his own fiancee at a young age.

Reincarnated 800 years later in the body of a young boy who shares his name, he found out his former fiancee already unified Kunlun’s Field and built the First Central Empire, and was now known as Empress Chi Yao… Empress Chi Yao—Her Majesty governed the mortal world and enjoyed prestige in all directions as well as an eternal life.

Zhang Ruochen stood outside of the Imperial Ancestral Temple, looking at the statue of Empress Chi Yao, and the flames of hatred burned in his heart. “After I practice for 13 years, I shall send the empress to her doom!”

- Description from Novelupdates

He was a school bully and she was a straight A student. One day, she received a message that he wanted to meet her after school. She was very scared of being bullied, so she sought help from her teacher, who was also his father. Therefore, his father came to meet him after school with a broom on hands and beat him up.“You little brat! How dare you bully the top student in our class! Just wait and see how I'll punish you!” said his father angrily.“No! Dad! This is a mistake! I just wanted to pursue her!”“You're clearly not good enough for her! Stay far away from her!”...Years later, in her wedding dress, she said to her best friend, “My husband used to be a school bully. He said that he was beaten up by his father on the first day he was planning to pursue me. Then, he was warned not to get in the way of my pursuit of Tsinghua University.”“Too bad! And what happened next?”“He also got into Tsinghua University.” She smiled.

A mysterious and strange world, a human civilization lacking power, and a horrible and turbulent world of human life, Luo Kai survived humblely as a prisoner. Pain and suffering honed his will. War and killing promoted his growth. He suddenly looked back. Is already one of the most powerful beings in this world.

- Description from novelbuddy