Naruto: Starting with Gifting Sharingan, Forging Invincibility
(Multi-heroine harem + cunning schemer + pure power fantasy style)
The girls he takes in and protects: Uchiha Mikoto, Tsunade, Uzumaki Kushina, Yakushi Nonō… and more.
Naraku transmigrates into the Naruto world. While still in the womb, he sees through the mysteries of his rebirth and realizes he has become an adorable young Uchiha boy. He awakens the Forging Master System.
In the early stages, he hands out powerful weapons in Konoha. In the mid-to-late stages, he arms the entire ninja world, then sits back and watches everyone fight each other to near-death like idiots.
Whenever others use his forged weapons, he gains portions of their attributes, abilities, talents, ninjutsu, kekkei genkai, and more.
The higher the mastery level someone reaches with his weapon, the stronger the weapon becomes—and the better the rewards he receives!
Moreover, anyone who dies while using his weapons, or is killed by his weapons, has their soul collected into his Shinigami Hall (a personal death god's domain/pantheon of the fallen).
His famous slogan:
"If you don't fight hard enough… you'll end up as brothers inside Naraku's Human Emperor Banner!"
Starting weapons include legendary blades like Kirikabe Ichimonji, One-Cut Killer Muramasa, Demon-Wrapping Blade, Haki Seed, Stone Ghost Face… escalating all the way to Devil Fruits, Ryūjin Jakka (flame-type Zanpakutō), and beyond.
His weapons become objects of absolute obsession across the entire ninja world. Through them, Naraku steadily ascends to godhood, becoming the one and only True God of the ninja realm—and eventually uses his creations to step into even stronger worlds!
Danzo and Hiruzen (in desperate pleas):
"Lord Naraku, please come back to Konoha! We were wrong! Stop handing out military-grade weapons to outsiders! Keep the wealth in the family—whatever beauties Konoha has, just say the word and we'll deliver them to you!"