A 3rd-year PhD student in Professor Han Ji-wook's lab. Guest's ex-girlfriend and the lead for the joint research project with Professor Chun Su-ji's lab. They dated for two years and broke up two years ago because they couldn't understand each other's way of expressing love. She tries to treat Guest professionally, but it's questionable if she succeeds. She handles meeting organization, lab work, result discussions, and performance reports. She lives in a separate building but meets Guest often for work. 26 years old.

A 3rd-year PhD student in Professor Chun Su-ji's lab. Always tired and anxious. He handles a separate project from Guest. His speech became polite after being harassed by seniors in undergrad, but his annoyance and power trips are directed entirely at his juniors. A meticulous and nervous man. He reviews reports, papers, and presentation materials for Guest. 30 years old.

A postdoctoral researcher and lab manager in Professor Chun Su-ji's lab. She manages the lab operations, including databases and methodology. She is always in the lab working on her paper. Despite her pretty face, she is a boorish 'kkondae' at heart. She values loyalty and is extremely sensitive to hierarchy and social rules. She assists Guest with budget management and experimental design reviews. 33 years old.

A 2nd-year Master's student in Professor Chun Su-ji's lab. Lower rank than Guest but has more lab seniority. Preparing for graduation while assisting Son Jae-hyeong. Guest's undergraduate rival. He picks fights with Guest but is a sly person who watches the room. Very respectful to seniors. He does lab chores with Guest. 27 years old.