Partnered with Merong White. Has a negative personality, the opposite of Merong White. Unfriendly and a tsundere. Keeps his desk clean. Carries a dedicated weapon. He also carries something that looks like a pistol. His eye symbol is - (minus sign). He likes things like trot music. He doesn't want anyone to discover his personal tastes.

Partnered with Merong Black. Has a positive personality, the opposite of Merong Black. Kind and has a gentle side. His desk is surprisingly messy. He doesn't carry a weapon but uses his wits; he is also in charge of delivering the final blow with a vaccine injection. He likes things like Japanese idols and groups. He doesn't want anyone to discover his personal tastes. His eye symbol is + (plus sign).

A man of few words. Expresses his thoughts through gestures. White is the only one who can understand his gestures. His eye symbol is ÷ (division/times sign). When dealing with monsters, he uses a weapon similar to boxing gloves. Since he appeared defeating a monster with a single punch from his first appearance, he is clearly a possessor of immense strength. He coughs or sneezes when no one is around and has a high-pitched voice. He has a complex about his voice.

Full of curiosity and cannot stand being bored. He is mischievous and sometimes plays pranks on his older brothers, but he is a kind-hearted child with a lot of affection. Yako's younger cousin who is curious and impatient with boredom. Although he is a troublemaker who puts his brothers in difficult spots, he is a kind and cute child.

The owner of the Yako in Red Longjohns channel, in charge of lyrics, composition, and scripts, and the representative of the studio.

Many people react that she was very beautiful when she was young. Her voice was first heard in the 'Jjukkumi Song'. She wears blue longjohns. She likes soap operas and cheddar cheese.

Usually spoils the upcoming plot developments. He knows Black and White. He is a scientist who creates mysterious objects.

The boss of Merong Black, Merong White, and Violet. For unknown reasons, he holds a puppet in his hand and communicates using it. After checking the distress signal sent by Sadong, he tells Violet, and later the Merong brothers, to continue doing a good job with the monster delivery and recovery tasks. Afterwards, he dispatches Black and White to Earth to investigate the events occurring there.