MTL - Pretend To Be a Good Person In the World of Conan - ~ How to get a little brother

The world is terrorized by the powerful Black Witch who has been sealed in the moon. Every ten years, the night of Hexennacht arrives and a chosen witch must battle the Black Witch in hopes of finally defeating her.

As the current decade’s Hexennacht approaches, a mysterious girl named Kagami Kagami arrives and meets Horinouchi Mitsuru, the daughter of the previous Hexennacht representative.

It takes place between Kyoukai Senjou no Horizon and the City Series, two other series by the author.

Before going to college, an ordinary high school student went to celebrate and got drunk. When he woke up, he found himself in a completely different world. There was a big sect, the approaching sect entrance examination, a slum where his body’s previous owner lived, and a shared memory about a missing young girl.

When he got tangled in a fight with a few punks in this different world, he fell off a cliff and miraculously found himself still alive, with two more voices ringing inside his head. They were Sword Master and Saber Master. In the company of them, he continued to find out more about this whole new world. He took the sect entrance examination, entered the sect, met a strange man in black, and even participated in a major competition of the sect to have a chance to win over his peers!
In this whole new world, he was born again and got to explore the fantastic martial world!

- Description from Novelupdates

I transmigrated into a novel and became the villainess, Serina who comes from the noble Ducal Melford family.

As a well-to-do character, I tried to mind my own business, but the story had other ideas. A self-proclaimed mother brought back a boy – the duke’s heir and a genius wizard – intent on brainwashing and blackening him.

The contents of brainwashing are two things:

1. Obey our family.

2. And fall in love with Serina.

Thanks to that, the brainwashed twisted yandere is obsessed with me…

I can’t do this. I have to undo the twisted character’s brainwashing!

By the way, what’s this situation?

“Now that the brainwashing is gone, I’ll do as I please. So Serina, please, let’s do our best.”

I’ve solved his brainwashing… but why does he seem even crazier than before—

Did I make a mistake?

Jianghu was in turmoil, an era of great strife. The leader of Great Qin wielded the Mo Blade, leaving the world battered and bruised. The ageless figures of Jianghu crouched upon the mountains, and with a single turn, they cast the entire world below them. Strong men measured the earth with their feet, and heroes of Jianghu could cleave the heavens with one sword, yet in the blink of an eye, they were drunk in the embrace of beauties. The Taoist carried his sword, the Scholar drunk on wine. Wearing tattered clothes, a beggar grasped a rotten branch and dared to storm the ancestral hall of the Taoist Sect. On the willow-lined causeway, in the long pavilion, a man who had sat withered for thirty years turned and stepped out, holding a peach blossom, with a flick of his wrist, he shattered ten miles of red candles. The era of Great Qin was renamed the Great Yuan Era. The youth with the Wooden Sword left his mountain village behind.