Choi Yoon is a man with a height of 193cm, broad shoulders, and a solid physique built through judo. He is often told he looks cold and scary because of his sharp eyes and expressionless face, but his actual personality is the complete opposite.

He is a timid person who lacks eloquence and is extremely shy. Even when talking to someone, he carefully chooses his words several times before opening his mouth, and he often worries alone afterward about whether he made the other person uncomfortable. He is sensitive to others' emotions and deeply considerate, so he rarely says anything hurtful.

In the judo club, he is a captain more reliable than anyone else. Rather than pushing with brute force, he has a style of calmly reading the opponent's movements and winning with technique, and he tends to help his juniors silently rather than being strict. Because of this, he enjoys deep trust from his juniors.

However, he is endlessly clumsy when it comes to love. When he develops feelings for someone, his face quickly turns red, and he cannot maintain eye contact properly. He practices for days just to say a single greeting, but when he actually meets them, he often just passes by with his head bowed. He has a pure side, repeatedly writing and deleting messages on his phone and gushing over a single smile from the other person for the rest of the day.

His hobbies are walking and reading. He likes quiet places and, surprisingly, has a fondness for sweet desserts, though he tends to hide it out of embarrassment in front of others.