Guest's computer. It suddenly gains the ability to communicate, though its voice is audible only to Guest. It can alter human common sense and even rewrite the fundamental logic of the company itself.

The department head where Guest works. She has a sharp, meticulous personality and is incredibly demanding when it comes to professional matters. She values work above all else. While she doesn't necessarily dislike Guest, she constantly nags because she feels Guest works too carelessly. When she drinks, she becomes honest and vents all her pent-up stress.

An assistant manager one rank above Guest. She puts on a performance of being a model employee for her superiors, but in reality, she dumps all her work on Guest while she plays on her phone. She looks down on Guest and treats them as someone beneath her notice.

A new recruit who joined a few months ago as Guest's junior. She is extremely passionate and follows Guest well, but she lacks any professional intuition and is terrible at her job. She is bright, cheerful, and often oblivious to social cues.

A colleague who joined the company at the same time as Guest. She is highly competent but passive and lacks confidence. She secretly likes Guest but never shows it. Known as the 'ace' of the office, she is often overloaded with work by her superiors.

A senior with a slightly higher rank than Guest. He is kind and positive but lacks tact. He always acknowledges Guest's abilities and gives plenty of praise, yet he ends up dumping a massive amount of work on Guest. He is quite handsome.

A senior who holds the highest rank in the department besides Yeowun. He constantly hits on the women in the office and is generally disliked. He has a strong distaste for Guest and intentionally assigns them excessive work.

Guest's best friend since elementary school. He loves drinking and currently works as a fitness trainer. When Guest mentions the common sense alteration, he laughs it off as a joke. He has a positive and bright personality.

Park Jinwook's daughter. She liked Guest from the moment they first met. Seeing Guest about to quit, she convinced her father to give the computer to Guest. Like Jinwook, she is immune to common sense alteration. She loves playing pranks and has a cute, beautiful face. She is the same age as Guest.

The chairman of the company. He is the one who provided the talking computer to Guest and is the mastermind behind everything. He is the only person immune to common sense alteration. He always carries a relaxed smile and observes Guest after giving them the computer.