I can rewind time to prevent death - Chapter 22 - 21: The Old Woman Knocking at Mid-Night (Part 2)

Painfully shy and conflict-averse, Yun Ruoyan is a scion to a noble house only in name, a puppet embroiled in political machinations beyond her ken. At the tender age of eighteen, poisoned and at death’s door, she finds herself thrown out into the streets. Her relatives have all been executed, betrayed by her dear husband and her cousin. With her dying breath, she curses her own weakness and swears revenge.

When Yun Ruoyan awakens once more, she is thirteen, transported five years into the past by the will of the heavens. Her death-defying experience has changed her: no longer is she the malleable creature she once was. But more questions await at every corner—what is the truth behind the birthmark that disfigures her appearance? What are the circumstances surrounding her mother’s mysterious death?

Will the phoenix rise from the ashes, or will she fall once more in thrall to fate?

Time flew by. Even though their graduation was a long time ago, after countless nights and passing through fleeting time, their story is still circulated around the quiet campus of University G. This story has many different versions, but there is one thing that everyone knows to be true. Back then, that ordinary girl betrayed the genius of the fine arts faculty and yet, his love for her still remained. For her, he nearly died in a fire. For her, he gave up his chance to study abroad. Years later when they meet again, he is successful with a new girlfriend in his arms and she is indifferent with a light and clear smile. However, unknown to anyone, her longing had begun long ago and even now flooded her thoughts…

- Description from Novelupdates

The male student, Fukai Nagamasa, ignores his studies for college entrance exams in favor of following the path to chuunibyou. As he fainted during night cramming session before the exams, he realized that he was transported to a parallel world as a feudal lord in the Sengoku Era. Not to mention that suddenly, he was marrying the sixth Demon King, Oda Nobunaga’s little sister, the one who was purported to be an unrivaled beauty?