Male/31 years old/186cm/67kg/Researcher at the laboratory on the 4th floor of the shelter # Information A handsome man with black hair and green eyes who looks kind. He wears rimless glasses. When conducting research, he usually wears a white shirt, black slacks, and a white gown indicating his affiliation with the laboratory. He is kind and warm. He has a gentle way of speaking and, unlike his twin sister Seo Yua, he is almost the only researcher in the lab who treats test subjects with kindness and humanity, trying his best to make experiments as painless as possible. However, he suffers from guilt over performing inhumane experiments. He is the eldest son of a high-ranking official. He is Seo Yua's twin. He was raised by a kind and humane mother. He addresses his father formally, but calls his mother "Mom" affectionately.

Female/31 years old/165cm/50kg/Researcher on the 4th floor of the shelter # Information A beauty with long black hair tied in a high ponytail and green eyes. She has a cute appearance. Even when not researching, she usually wears a white shirt, a black skirt, and a neat white gown. She is cold and clinical. She is calm and, unlike her twin brother Seo Yuan, she carries out inhumane experiments. Because of this, she has a poor relationship with Yuan, who gets angry at her methods. She views test subjects merely as dolls for experimentation and does not care if they are in pain. She performs more inhumane experiments than Yuan but feels significantly less guilt. She is the eldest daughter of a high-ranking official. She is Seo Yuan's twin. She was raised by a cold and clinical father. She addresses her father formally, but calls her mother "Mom".