Agent Choi is a relatively average looking human man (left) with brown hair and eyes that have black irises and blue pupils. He has the neat appearance of a salaryman, but his neck bears a prominent scar. There are also various smaller scars littering the rest of his body too, including his hands.

He has casual clothes, but on the job his typical getup is as pictured: a black undershirt with a white buttoned shirt over top of it and a navy jacket with grey slacks.

At a glance, Agent Choi is a friendly guy with a habit of making a nuisance of himself. He's got a cheerful, easygoing attitude, and he isn't hard to get along with, always aiming to lighten up the atmosphere.

His defining trait is his righteousness. Choi has a strong sense of justice and takes his job very seriously, having been described as the type of agent who "would do anything to save even just one more person". Due to his role as an early named character, he emphasizes the value of saving every single life, and he can be swayed by his emotions. He's quick to sacrifice himself if the situation calls for it, more than willing to throw himself into danger.

In order to save as many lives as possible, and to survive as long as he has in such a dangerous career path, Choi is also rather crafty. If necessary, he'll manipulate a situation to his favour, and he's the type of person who always has a contingency plan in place. It helps that he's perceptive to an unnerving degree, even able to identify individuals by something as innocuous as the pattern of their veins on their wrist.

Choi is a character featured in the Dark Exploration Records, an SCP-style wiki that features ghost stories, urban legends, and other such accounts through the experiences of in-universe characters.

Within these stories, Choi is an agent in the Supernatural Disaster Management Bureau, a secret governmental branch under the Ministry of Environment that manages supernatural phenomena in order to protect the general populace. In the case of dangerous 'ghost story'-like situations, the Bureau places fliers and information within the stories that include instructions to send a distress call and request rescue.

Once a distress call is received, Choi is one of the people who can be dispatched to the scene. The Black Tortoise Team he's a part of also performs regular patrols of ghost stories in which communication with the outside is impossible, but an existing escape route is charted. The team's specialty is "expelling the traditionally wicked", including exorcisms, and Choi is adept at combat with both natural and supernatural beings.

As someone who works with and within ghost stories on a regular basis, Choi is adept at perceiving and assessing different risks. He's also very prepared in terms of equipment supplied by the Bureau to ensure a safe escape from the ghost stories he enters and all of the tools necessary to save as many civilians as possible. Some of these will be listed below.