Sui-Tang: Inheriting the Overlord's Legacy, Empress Xiao Says I'm Fierce

[Broken Engagement from the Start] + [A Showdown with Li Er] + [Rebuilding the Sui Dynasty] + [Pacifying the Four Barbarians] Yang Zheng unexpectedly transmigrates to the Sui Dynasty in the twelfth year of Daye. He plans to head south to Jiangdu and join Yang Guang, using Yang Guang's support to gradually build his own power before embarking on a quest to conquer the realm. But before he can set off, he unexpectedly falls in love with Li Xiuyan, Li Yuan's sixth daughter. Hoping to win her hand, he abandons his dream of conquering the realm and instead becomes one of Li Yuan's advisors. Drawing on his knowledge of Sui and Tang history, Yang Zheng repeatedly performs great deeds and renders invaluable service to the Li family. In return, Li Yuan promises that once the Li family has pacified Guanzhong, he will formally give Li Xiuyan in marriage to Yang Zheng. But just before Li Yuan is about to ascend the throne and declare himself emperor, he publicly breaks the engagement, citing Yang Zheng's humble origins. Only then does Yang Zheng realize that the supposed love between him and Li Xiuyan was a scheme against him all along. Faced with the Li family's treachery, Yang Zheng unexpectedly awakens the Turbulent Times Choice System. He gains the martial prowess of Xiang Yu, the Hegemon-King of Western Chu, and learns that he is actually the grandson of Yang Yong, the deposed crown prince, making him a true member of the Sui imperial clan. Now that he has a System, Yang Zheng has no reason to go easy on Li Yuan. In the early hours before the enthronement ceremony, he takes Li Jiancheng hostage, rescues Li Jing from prison, castrates Li Yuanji in front of Li Yuan and his ministers, then walks away without looking back... As long as he is here, the Great Sui will never fall. And the one who destroys the Tang will be Yang Zheng.