DB Vol 6 Part 3

Seo-na realized that the source of this chill was a sound that was inaudible to human ears and utterly overwhelming. Sound. There was only one person in front of her capable of wielding power related to this ability. Seo-na trembled unconsciously, only to realize belatedly that the people around her had collapsed to the ground. Strangely, only the Espers had fallen.

Many were unconscious, eyes rolled back and foaming at the mouth, while the others who barely held on were slumped over the floor vomiting or pissing themselves without even realizing their pants were wet. Among the Espers, Seo-na was the only one unscathed. Suppressing her tension, she looked up at Gye Yoon, who had almost reached her.

To physically neutralize Espers so instantaneously. However, there was another reason why Seo-na was particularly appalled. Out of all these people, Gye Yoon had selectively attacked only the Espers. It would have been easier to simply blanket the entire area with power—just releasing it with all one's might.