Zen would often confide in his older brother, who would explain that his mother was only saying those things to 'protect him' from being used by others due to his handsome appearance. He would often be treated poorly by his parents, specifically his mother, who questioned who he got his looks from and frequently called him ugly, causing a rift to form between the two. During his younger years, he was harassed by strangers as they followed him to touch him or take pictures of him.

His family is described as being quite conservative his parents being teachers and his older brother working as a lawyer. Zen is the youngest son in his family, and lived with his mother, father and older brother. He is shown wearing multiple outfits, including a grey jacket with large buttons and a logo feature, a black turtleneck, tight fitting pants and black formal shoes. Zen's eyes are pinkish-red and almond-shaped. He has silver-white long hair with short bangs falling slightly over his eyes, and his hair is tied in a low ponytail which reaches down his back. He is 182 cm (5'11') tall and his weight is 75 kg (165.3 pounds). Zen is a tall young man with noticeable muscle tone due to regular training. Like many of the members, he has scars from his past which can't be forgotten. He is known for pursuing larger and better musicals, offering up smaller ones or turning them down if the opportunity presents itself. He can be easily upset if something affects his career, almost entering a depressive state.

In conjunction, deep down Zen self doubts himself, wondering if people only see him for his looks, rather than his talents. He usually calls them 'sweetie' or 'babe'. While Zen likes to compliment himself, he often flirts with MC. Despite this, Zen can become very loyal and caring, especially to those he cares about. Zen tends to compare others to himself when it comes to looks, frequently telling Yoosung to work out to look half as good as he does. He will often talk about his looks, praising and complimenting himself for how attractive he is, as well as how talented he is when it comes to singing and acting. On the surface, Zen is known for being a very eccentric and flirtatious character.

Mystic messenger