Yoo Joonghyuk has wide black eyes with thin double eyelids and thick eyebrows. His right eye glows golden upon activation of the skill [Sage's Eye]. His hair is black and slightly wavy, cut short. He has tan skin, a sharp nose ridge, and a strong jawline. He is extremely muscular; in particular, he has well-toned biceps and thighs. He was originally a caring person at heart, doing good where he could, but repeated regressions have worn him down to the point where, he kills off everyone. 