DxD: System of the Harem King - Chapter 106: Six and Nine

Lin Luoran is a 27-year-old girl from a rural family. She doesn’t have a college degree, let alone any money.

He is a young man without a spirit root. It is believed that this denies him the chance at cultivation. However, a mysterious lady imparts a Supreme Demon Classic to him and from then on, he starts his path of cultivation.
He undergoes a total transformation to emerge as the most fearsome and powerful fiendish demon in his era, that even immortals and fiends are fearful of him, and saints are at his beck and call.
Mastering the Supreme Demon Classic is the turning point in his life. He is able to unleash his immense and divine power from within, illuminating the entire universe!

- Description from Novelupdates

The Red Dragon came from the vast wild wastes, coveting all the strength in the world. It once had countless titles: Mountain's Wrathful Flame, Infernal Calamity, Crimson Emperor, Ashen Dragon......The world trembled under the shadow of the giant dragons. He stirred up the craze of the magic industrial revolution; in the empire he established, Wyverns roared, artillery fired in unison, and steel beasts appeared in the sky and on the land, while disasters from another world rampaged everywhere.“Submit, or die.”Cassius spread his wings, blotting out the sun, and gazed down at the trembling humans, elves, and dwarves below, saying thus.......It is a story about a Red Dragon with a player template conquering, ruling, and transforming an alternate world.(Pseudo of DnD, The Fourth Calamity, Red Dragon)

The magical girl who made the wish of “destruction of this world” came to Ke Xue’s world, and Kewpie became a little Kewpie.

Being chased by someone holding a knife at the beginning, Shuangyue fell silent.
In a world without witches, how would she purify her soul gem?

Originally, he just wanted to be a good and hard-working employee in the winery, but the old man always liked the whole brainwashing operation. Suppressed by the world consciousness, for her own pure land, Shuangyue decided to go to his red square and black square, she would smash the dog world consciousness.

The protagonist is not a good person (highlighted), the three views have been distorted in the magic circle world, not a red square.

Little Cupid: You are my magical girl, and I am your Cupid.
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Rescuing Matsuda Cat and Jingguang Cat, the protagonists directly built a gray empire for Jin Jiu and Sister Bei.
Hagihara and the squad leader are still dead, because the protagonist was not there at the time.
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Do not dismantle the original cp, bring your own cp (but there is no obvious emotional line).

Content Label: Teen Conan
Search keywords: Protagonist: Frost Moon Saya ┃ Supporting roles: Gin, Zhufu Jingguang, Matsuda Jinping, Edogawa Conan, Maorilan, Kayao (Shirazawa Nozomi), Little Cupid (Ruby) ┃Others:

- Description from novelbuddy