Global Reincarnation: Only I Know the Plot - Chapter 964:

Getting the [Boosted Gear] is expected for Issei. What if he gained it a month early and another one as well? Let the Games Begin... IsseiXHarem (if it wasn't, it wouldn't be DXD). Now has a TVTropes page! Getting the [Boosted Gear] is expected for Issei. What if he gained it a month early and another one as well? Let the Games Begin... IsseiXHarem (if it wasn't, it wouldn't be DXD). Now has a TVTropes page!

Transmigrating to the disciples of the Demon Sect, and relying on the skill modifier to become a giant of the Demon Dao.

[Detected the technique “Blood Nerve”, relying on devouring blood to practice]

[Side effects: easily affected by the spirit contained in the blood, becoming bloodthirsty, bloodthirsty, mad, and even brain dead]

[Please wait a moment, the system is being modified…]

[Ding! The modification is complete, and the side effects are cancelled]

- Description from novelbuddy

Cheng Yujin was the elder twin sister, who was supposed to be engaged to an excellent man. However she later learned that her fiance, Marquis Jingyong, had proposed to her because he mistakenly recognized her as her younger twin sister. Marquis Jingyong and her younger sister had a deep relationship, and after many twists and turns, finally broke through all hardships and became eternal lovers. While Cheng Yujin was the villain who replaced her sister’s good marriage, kept framing her sister, and hindered the main couple to be together. A really wicked older sister and poisonous ex-wife.

After the younger twin sister was reborn, she revealed Cheng Yujin’s ‘conspiracy’ early on. Everyone scorned her, and her so-called fiance was indifferent. Cheng Yujin sneered and tore off their engagement letter in front of her fiance.

Everyone was gloating and happily waiting to see her regret her actions. However, before Marquis Jingyong had a chance to see Cheng Yujin’s regret, he saw his former fiancee marrying her uncle.

The ninth uncle of Cheng family was truly a hidden dragon, his real power frightening everyone.

***

Cheng Yujin, this coquettish little wife, lightly lifted her eyebrows and casually said, “A mere Marquis Jingyong, is he worthy? Do you think that robbing him away will affect me?”

Almost forgot to say, ninth uncle wasn’t surnamed Cheng. His real name was Li Chengjing, the crown prince.

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