This is The Strongest Characters in the World Are Obsessed With Me.
One day when she was thirteen years old, while chewing bread as a snack, Dalia Pesteros suddenly remembered her past life. This is an impoverished otome game world where the main characters go crazy, and she was born as the sister of the worst villain in the future! There is no solution at this rate. The family will be exterminated, and I will be thrown away. So, no matter what, I must get out of this family as soon as possible! ‘Now that it’s like this, I need to lower their guard and run away.’ In order to get rid of the relatives who aim for the family and the sly emperor, it’s better to be in good favor with my brother- “I want to dance with Dalia. What’s the problem?” “I’m sorry, but my sister is shy.” “Dalia said I was her favorite!” Somehow, it’s not only my brother that I tamed, but all the strongest characters in this world are obsessed with me!
The protagonist is reincarnated in the world of an otome game she'd been playing. She wakes up in the body of Dahlia Pesteros, a 13-year-old girl whose 16-year-old brother, Hikan, is the heir to a Duke and a future villain of the game.
The story is set within the Frederick Empire, which was once blessed by a dragon. As a result of that blessing, one member in each generation of the Imperial Family and those of the Four Major Duchies is born with magical powers. These individuals are known as 'Transcendentals,' and while their mental and physical abilities are far superior to those of average people, the more they use magic, the more their souls are corrupted, causing them to eventually go berserk. At that point, only the other Transcendentals can stop them. The Emperor is a Transcendental, as is Hikan.
Hikan and Dahlia's mother died not long after she was born and, in the second chapter, he informs her that their father has passed away as well. At the father's funeral, some older relatives approach the pair and suggest that one of them should act as a proxy for their late father until Hikan turns 18, but he rejects the offer.
In chapter 5, we're introduced to the Duchess of Blueport, a Transcendental in her forties who wears gloves and a face mask to conceal the burns she received during a fire that killed her husband. It's shown in flashbacks that she helped to care for Dahlia after her mother died.
In chapter 20, preparations are being made for a ball to celebrate Hikan being appointed as the new Duke of Pesteros by the Emperor. Dahlia learns that her lady-in-waiting will be Adalicia Benitez, the original female lead of the game who was raised as an assassin and currently works as a spy for the Emperor.
In chapter 27, the Duchess of Blueport starts to go berserk at the ball and surrounds herself with a dome-shaped force field to contain herself and keep everyone else away. Adalicia tells Dahlia to leave and then enters the force field, but rather than leave, Dahlia enters the force field as well. Once inside, she hugs the Duchess of Blueport, which causes the Duchess' outburst to subside and the force field to dissipate. Having witnessed this, the Emperor concludes that Dahlia has the power to purify the souls of Transcendentals through physical contact, thereby reversing the spiritual corruption that causes them to go berserk.