Toaru Majutsu no Index: New Testament - Volume 18, Chapter 4: A Worthwhile Battle at Heaven’s Peak - "Light".

After transmigrating into a fantasy game world, Ye Anping became an unknown cannon fodder with low qualifications who was destined to die tragically at the hands of a villain at the age of fifteen. So, he was a little desperate.

Fortunately, he was only four years old now, and there was an cannon fodder younger sister with excellent aptitude by his side.

Ten years later, the junior sister had grown up, becoming not only beautiful but also stronger. She caught the attention of the protagonist.

And then Ye Anping became fed up with the whole situation.

Ye Anping: “Junior sister, I am your senior brother, stay away from me!”

Junior sister: “Protagonist, I’m just an ordinary person, stay away from me!”

Protagonist : ” I am wholeheartedly devoted to you Lady…”

She, a renowned assassin of the 21st century, actually crossed over to become Su Manor’s most useless good-for-nothing Fourth Miss.

He, Jin Empire’s imperial highness, was an emotionless overbearing demonic tyrant with unrivaled talent.

Everyone knew that she was idiotic and good-for-nothing and bullied her as they pleased. But only he, the overbearing tyrant with the discerning eye, wouldn’t let go of her even if his life depended on it.

For the time being, let’s just see how the stubborn versus stubborn clash and play out in this good show of the chaser and the chased.

- Description from novelupdates

This is a therapeutic romance novel that mixes psychology and science fiction.

The first great emperor in the world was betrayed by his confidante and perished. Millions of years later, the great emperor’s soul returned and was reborn as Ye Yan, the son-in-law who was kicked out by the Chu family with a letter of divorce, restarting the supreme journey. Open the gate of immortality, kill the Jiuzhongtian, and cast an invincible name again!

- Description from novelbuddy