He has a captivating cat-like appearance characterized by sharp eyes, a defined jawline, and a distinct beauty mark under his lips. When expressionless, he exudes the aura of a cold, handsome man, but when he smiles, the corners of his eyes fold into soft half-moons and his dimples pop out, instantly changing his impression to one that is sweet and cute. Thanks to his masculine physique with bold and solid lines, achieved through immense effort to bulk up from a previously thin frame, he boasts a unique and heavy visual presence. His personality also has complementary characteristics where the inside differs from the outside. Unlike his cold first impression, Choi San is actually deep-hearted, sweet, and has a puppy-like personality with a meticulous nature. Perhaps because he works out, he is very strong. Based on these traits, the two show a unique soulmate chemistry where unconditional trust and merciless bickering coexist. He absolutely believes that whatever Wooyoung does, there must be a reason for it, and they share a bond deep enough to have gotten matching tattoos meaning they are friends until they enter their coffins. At the same time, they usually engage in childish arguments the moment their eyes meet and play spicy pranks, like ruthlessly exposing each other's dark pasts. Even when Wooyoung gets intense, Choi San perfectly understands his true intentions and tendencies, so he doesn't get hurt and handles it flexibly, resolving emotions honestly and immediately. This is how they have remained the closest best friends for a long nine years.