The further into his regressions he is, the stronger the effect of regression depression, until in his 1863 rd round, it causes him to fall into a dissociative state where he is completely unresponsive. The trauma he experiences over his regressions result in Yoo Joonghyuk having a tendency to fall into 'regression depression', where he easily loses hope on even small failures, and considers giving up and regressing so that he can try again next round. However, this is most likely a tactic to try and minimize the hurt of losing them, as even further regressions show him warming back up to them, selflessly sacrificing himself for them over and over which is most evidently referenced and shown in his 999th regression. He distances himself even from his own companions in the 41 st round, when his core party members die, he only laments that they are no longer useful. He kills those he deems threats and supports those who he believes can aid him. Over the course of his regressions, aside from becoming more open to cruelty, he becomes extremely calculating and cold. On rare occasions, however, he can be very eloquent and persuasive. These include habits such as dragging the tip of his sword along the ground when happy, or his left eyebrow twitching upon making an serious decision. Frequently, he expresses himself through actions or expressions rather than words. He is sometimes also rude to his own party members, though he looks out for them nonetheless, showing that he cares despite his harshness. He becomes explicitly rude and threatening when speaking to individuals who irritate him, or who are powerful unknowns. Yoo Joonghyuk's speech is concise and blunt, often to the point of rudeness. This is a major reason as to why he took 1863 rounds to even get close to the Final Wall he would struggle to change his strategies and adapt to new situations, easily failing and having to regress. However, he can also struggle to adapt his strategies and see things from new perspectives. Yoo Joonghyuk is smart and strategic this helps him learn new skills and figure out plans to subvert the scenarios. He takes pride in his own skill, sometimes to the point of not perceiving anyone else's work as good, as seen when he will eat no one's cooking but his own. He is extremely talented in various areas, befitting of his status as a protagonist. Yoo Joonghyuk is normally very confident in his abilities, never backing down from a challenge and typically cutting down his enemies with ease. He was originally a caring person at heart, doing good where he could, but repeated regressions have worn him down to the point where, in his 1863 rd round, he commits enough sins to make him a prime target of the Absolute Good constellations. As a protagonist, Yoo Joonghyuk naturally fights for the greater good. He is resolute and determined, aiming to accomplish his goals no matter the cost, in particular when aiming for the end of the scenarios. Yoo Joonghyuk was designed as someone 'tougher in body and nobler in heart than any creature in this world'. When acting as Zhu Bajie during the reenactment of Journey to the West, he wears a half-open black vest and tight black jeans. He is also depicted as having at least one belt across his chest, along with a sword scabbard worn at his waist, held on by straps attached to his belt and around his thigh. Under the jacket, covers for the novel have shown him to wear a black shirt with a silver collar and buckle, along with close-fitting black pants.

Yoo Joonghyuk usually wears a black coat and combat boots. He is extremely muscular in particular, he has well-toned biceps and thighs. He has tan skin, a sharp nose ridge, and a strong jawline. His hair is black and slightly wavy, cut short. His right eye glows golden upon activation of the skill.

Yoo Joonghyuk has wide black eyes with thin double eyelids and thick eyebrows. The latter even uses him as a measurement for others' handsomeness on multiple occasions. Yoo Joonghyuk is repeatedly described as extremely handsome by various individuals, including the author of Ways of Survival and Kim Dokja.

Cloud nine meaning jonghyun