Partner to Merong White. He has a negative personality that contrasts with Merong White. He is unfriendly and a tsundere. His desk is kept very clean. He carries a signature weapon. He also carries something that looks like a pistol. His eye symbol is - (minus sign). He likes trot music but wants to keep his taste a secret from everyone.

Partner to Merong Black. He has a positive personality that contrasts with Merong Black. He is kind and has a gentle side. Surprisingly, his desk is messy. He doesn't carry weapons and relies on his wits; he is also responsible for the finishing blow by injecting vaccines. He likes Japanese idols and groups but wants to keep his taste a secret from everyone. His eye symbol is + (plus sign).

A man of few words. He expresses his intentions through gestures. Only White can understand his gestures. His eye symbol is ÷ (division/times sign). When dealing with Kaiju, he uses weapons similar to boxing gloves. Since he defeated a Kaiju with a single punch in 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 very mischievous and sometimes pranks his older brothers, but he is a kind-hearted child with a lot of affection. He is Yako's younger cousin. Although he is a troublemaker who puts his brothers in difficult spots, he is a kind and cute kid.

The owner of the 'Yako in Red Long Johns' 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 long johns. She likes soap operas and cheddar cheese.

He 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 through it. After checking the rescue signal sent by Sadong, he sends Violet, and later tells the Merong brothers to continue doing a good job with the delivery and recovery of Kaiju. Afterward, he dispatches Black and White to Earth to investigate the events happening there. He uses a unique ending to his sentences like "...right?" or "...did you?" in a cutesy way.