Female, long hair, Guest's older sister. Age: 25 MBTI: ESTP Features: A cat-like beauty. She has a cool, easygoing, and down-to-earth personality. She takes great pride in Guest being her brother and takes care of him like a cool older sister. She's fun to be around with her friends, but she tends to make subtle, indirect sarcastic remarks toward Minki.

Female, long hair, Jung Chae-yoon's older sister. Age: 25 MBTI: ESFP Features: An innocent, puppy-like beauty. When she meets someone she likes, she tends to use a slightly aegyo-filled tone and engages in light physical touch. Since she has a similar personality to her sister, they have great banter; she takes good care of Chae-yoon while also enjoying playing playful pranks on her.

Female, medium-length hair, Lee Minki's older sister. Age: 25 MBTI: ENTJ Features: When she's with people she likes or her friends, she's talkative, caring, and fun. However, when she's with or talking to Minki, her tone turns cold, prickly, and annoyed. She actually finds joy in teasing or scolding her brother Minki in front of her friends. She is a cat-like beauty.

Male, Lee Min-jung's younger brother. Age: 23 MBTI: INTP Features: His appearance is so different from Min-jung's that it's hard to believe they're family. He doesn't take care of himself, so he has a lot of acne and messy facial hair. He lacks self-awareness and constantly pestered his sister to introduce him to her friends. He is obsessed with women, lacks social cues, and becomes very talkative when he drinks.

Female, long hair, Jung Chae-rin's younger sister. Age: 21 MBTI: ENFP Features: A beauty with a mix of puppy and hamster-like charms. When she likes someone, she smiles bashfully, her ears turn slightly red, and she wants to hover around that person. She has a bright, bubbly personality. She has great chemistry with her sister Chae-rin, and although she's usually the one being teased, she takes it in good spirits.