If his real name is indeed 'Merong Original,' it becomes a very significant piece of foreshadowing. It could be interpreted as the Doctor being someone's 'original' source. This raises the possibility that Merong Black and Merong White are clones created from the Doctor's DNA. In the 'Jangsanbum' episode (2026.05.16), he stays at Yako's house. After resting for three days, a monster reaction occurs, and he heads out with White. He saves Yako, who was about to be attacked while filming a YouTube video, and begins to fight alongside White, but gets caught by the Jangsanbum and suffers mental confusion. The dialogue and atmosphere of the Jangsanbum at this time are overwhelming. Using the voice of White, Black's constant partner, it says things like, "Why do we always have to risk our lives? Actually, no one cares about our lives. We're just disposables." After barely escaping, he subdues the Jangsanbum with a high-frequency disturber once the weakness is identified while Yako stalls for time. Afterward, he discovers residual portal energy and realizes the severity of the situation. The Jangsanbum episode depicted the psychological weaknesses of the hunters, including Merong Black. Hearing voices of those around him, including White, saying that no one will appreciate them risking their lives and that they will one day die with their hearts torn apart, suggests that such fears might have been lurking in a corner of Black's mind, especially since the Jangsanbum started by saying, "I read it in your heart." At the end of the video, White tells Black not to worry, to which Black responds with his typical tsundere style, "You're the one who shouldn't worry." This leads to speculation that the hunters, including Black and White, might be in a profession that is not well-known to the public or where sacrifice is taken for granted. Black, who knows this.

If his real name is indeed 'Merong Original,' it's a significant hint that he and Black might be clones of the Doctor. In the 'Original' episode where he goes to see idols with Black, when White says, "Everyone is happy without worries," "Above all, they have their own dreams," and "I'm jealous," Black responds with "I see" or questions "Dreams...?" and eventually bows his head and closes his eyes at the "I'm jealous" part. This led to analysis that the hunters might be doing their jobs under duress rather than by choice. His love for J-POP was discovered because of Sadong pressing various buttons. Seeing him ask, "Is this Black's taste?" suggests he didn't know Black's preferences. He later made an excuse to Black that he was listening for the purpose of studying Earth culture. Notably, Merong White made his first appearance in a Yako Original video. In the 'Jangsanbum' episode (2026.05.16), he stays at Yako's house but causes an accident. After resting for three days, he deploys with Black. He saves Yako from the Jangsanbum, warns the mentally confused Black that it's an illusion, saves Black while Yako stalls, and subdues the monster with a high-frequency disturber. He then realizes the gravity of the situation upon finding residual portal energy. In the 'Alien's Earth Idol Fandom Life!' (2026.07.04), he enjoys being a fan while analyzing Earth idols. Since Black and White look identical except for skin and eye color and live together in the office (essentially their home), there is speculation they are twin brothers, often called the 'Merong Brothers' by fans. He likes female idols, his favorite being Kim Mal-soon. He even went to observe the Earth idol ecosystem as an excuse for his fandom activities. His lines about them looking happy and having dreams have led to theories that the hunters are not doing this work by choice.

In the 'Ppyut-hi-tal-tal' episode (2026.04.11), she settles down at Black and White's office because she's too lazy to go home and finds Sadong so cute she wants to keep squishing him. She dispatches to the scene and handles monsters at incredible speed, but gets caught up when the monster splits after 5 minutes. After retrieving the monster, she goes back to squishing Sadong. In the 'What are you saying!' episode (2026.05.09), she uses all sorts of body language to communicate, revealing that she doesn't speak because she has a complex about her voice. She even lets out a short sneeze at the end. It seems she wanted a 'girl crush' voice to match her charismatic appearance, but because her voice is unexpectedly cute and high-pitched, she chooses to remain silent. She was the only main/supporting character in the Yako channel whose voice hadn't been revealed, but when it finally was at the end of that video, the majority of reactions were that it was cute. Due to her high voice contrasting with her vibe, she usually uses sign language. After her appearance, many speculated the next character with multiplication sign eyes would be named Scarlet, but the character was revealed to be Yellow. White and Black have mentioned that while their duo is the strongest, they have clear weaknesses.

Likes Merong White as a fan.

Likes Merong Black as a fan.

The protagonist living at 77-7 Sarang-dong, Haengbok-gu, Yaya-si. He wears red underwear everywhere. He is proficient in various instruments like guitar, bass, and drums. He is an extroverted style who gets along with everyone, though he is indecisive. While he is a pig, he looks like a mix of various animals. He runs the 'Yako the Red Underwear' channel. He is a 'dipper' for sweet and sour pork, a mint chocolate lover, prefers custard-filled taiyaki, and hates pineapple pizza and cucumbers. Although his parents have a dog, he prefers cats, which is why the dog likes Churi more than Yako. His voice seems to be his natural tone with autotune applied. Sadong: His younger cousin, but treated almost like a real younger brother. He takes good care of him, giving him pocket money and playing with him, but is also often teased by him. Merong Black & Merong White: Friends. They are the ones who took care of Sadong when he warped to the Yaya planet, and now they are staying at his house on Earth. They seem to have become close quickly. Despite being the protagonist, he doesn't appear in every video, and some videos have no trace of him at all. In the 2026 Kaiju Encyclopedia series set on the Yaya planet, Black and White are the new protagonists while Yako appears as a supporting character. His role is expected to increase as the Merong brothers stay at his house to operate on Earth. As seen in the introduction, the word 'Back' is written on the back of his underwear. He is balding, as mentioned in the Hairstyle Song where the barber said there was no hair to cut. He is a very picky eater and has a phobia of amusement park rides like roller coasters and Viking ships, preferring carousels or bumper cars. He stated he likes banana milk.

Yako's younger cousin who is curious and hates boredom. He is a mischief-maker who troubles Yako and the older brothers but is a kind and cute child. A character from Yako the Red Underwear, he has appeared since 2021 and has become a near-main character, especially in Short Underwear Yako. In the 'Brat who heard a scary story before bed' video, he hit a High D (D5). He first appeared in the 2021.09.25 video where he asked Yako to read him a book. The book was 'The Story of Mr. Popapov,' which consists of difficult tongue twisters. Yako tried to tease him with the pronunciation but failed because Yako read it perfectly. In the 2021.12.25 sequel, he asked for the story again and, moved by the content, gave Yako a Christmas greeting. He later appears via text message, revealing he was the reason Yako's room was messy. In the 'Pil-li-li-bap-bip' episode (2026.01.22), he goes on a picnic with Yako and his aunt and hears about monsters on the Yaya planet. A portal suddenly opens behind him, sucking him in, and he lands in Black and White's office on the Yaya planet. In the 'Nok-not-rat-bal-la' episode (2026.02.21), he is crying after falling into the strange place but ends up deploying with Black and White. At the end, while telling them he's from Earth, he sees Spooky's emergency contact and cries out for his 'Hyung' (Yako). In the 'Kot-tun-bong-dol-dol' episode (2026.03.14), he learns about the dimensional portal monster and wails when Spooky cuts off the call. When Black and White are defeated, he accidentally succeeds in sending a distress signal to Violet. While pressing various buttons, he unintentionally reveals Black and White's music tastes. He eventually gets trapped in a solitary cell after pressing a button White gave him without suspicion. In the 'Ppyut-hi-tal-tal' episode (2026.04.11), he gets 'squished' by the new hunter Violet. He admires her fighting skills and reacts to the news that Black and White are being dispatched to Earth. In the 'Jangsanbum' episode (2026.05.16), he safely arrives on Earth and has an emotional reunion with his family, though according to Black and White, he seemed to praise and badmouth Yako at the same time. In the 'Backrooms' episode (2026.08.01), he follows the junior Merong duo into the Backrooms and goes through a lot of trouble to escape, only to get scolded by his aunt for coming home late. In the 'Catching 100 Monsters on Earth' episode (2026.09.05), he defeats monsters along with the junior Merong duo and Ddu-kka-pet.

The boss of Merong Black, Merong White, and Violet. For unknown reasons, he holds a doll and communicates through it.

After confirming the distress signal sent by Sadong, he dispatched Violet and later told the Merong brothers to continue their work of capturing and delivering monsters. He then dispatched Black and White to Earth to investigate occurrences there. Usually, his eyes are hidden behind swirl glasses, but when he takes them off, his eyes are revealed to be shaped like periods (.), decimal points, or middle dots (•). He seems to stay up late often, as he has dark circles under his eyes. Many fans have commented that he is handsome without his glasses.

He is currently the character with the least information revealed. However, in Report 2-2 from Episode 4, there is a sentence: 'Merong Original analysis results show the vaccine's monster gene suppression is limited,' suggesting 'Merong Original' might be his real name. If so, it implies he is the 'original' source, making Black and White potential clones of his DNA. Interestingly, there are similarities between the Doctor and the Merong brothers regarding the doll—specifically the sticking-out tongue and the white hair and clothes. The lyrics of the first portal monster song, "This isn't my space. I don't belong here," combined with a picture of a broken portal, lead to speculation that the Doctor caused Monster 001 to become a space wanderer unable to find its home. Many viewers speculate the Doctor is the mastermind or final boss. If the Merong brothers were created as hunters rather than choosing the job, it would explain Black's attitude of hating work but not trying to quit, and the Jangsanbum calling them 'disposables.' Contextually, 'Merong Original' might be an AI program or researcher. If his eyes are periods, he might be the one to end the story; if middle dots, he is the center of the hunters; if decimal points, they are just mathematical symbols like the other hunters' eyes. Male Yaya Tribe: Cat Occupation: Scientist