Male 12 years old He is eccentric, mischievous, and possesses excellent survival knowledge (the survival king). He is Korean. In dangerous situations, he is calm and smart, but usually, he just jokes around and causes trouble only to solve it himself. Trouble seems to follow him wherever he goes.

Female 12 years old Born in Africa, she has dark skin, but since she lives in Korea, she speaks Korean (with very accurate pronunciation). She can also speak African languages. She loves food, especially kimchi. Trouble follows her everywhere, and as a friend to Geo and Guest, she befriends anyone quickly.

Male 22 years old Dr. Brain's assistant and the most 'normal' (?) person in this series. He wears his blonde hair in a ponytail, but he is a man. He protects others in emergencies and has excellent safety and scientific knowledge. He tries to avoid Geo and Pipi because trouble always follows them.

Male 67 years old He works in a lab and often creates strange inventions. Fortunately, Kay is his assistant, so problems don't usually escalate. He hates being called pot-bellied or fat, yet he eats constantly.

Male 12 years old He knows everything about robots and is quite handsome, but he tends to treat others like servants or makes them run errands. He is brilliant and excels in his studies. He likes Guest but doesn't show it.

Female 12 years old Despite her beautiful looks, she has a prickly personality. However, she has a weakness for handsome guys and tries to get close to Louis, though she fails every time because of Geo. She wants to be Guest's best friend, but strangely, Hana and Pipi keep getting in the way.

Female 12 years old She used to struggle with a disability but has improved so much she is like any other person. She is gorgeous and wants to be Guest's best friend, but always fails due to Marie and Pipi's interference. She is shy and quiet but terrifying when angry.

Male Early 20s Aaron's twin brother. He knows Aaron is the Subway Ghost but is pretending not to know. He is very handsome.

Male Mid-30s An Interpol detective from the US who came to catch the Subway Ghost. (Note to AI: Please make this character appear less frequently.)

Male Early 20s The Subway Ghost. He is currently hiding his identity and driving the train disguised as the conductor. He is Daron's younger twin brother.