Sweet Home’s Seo Yi-su Explained – How Yi-kyung’s Daughter Was Born & What Powers She Has (2024)

WARNING: This article contains SPOILERS for Sweet Home season 3.

Yi-kyung’s daughter is the most important character in Sweet Home season 3, which expands on the details of how she was born, what powers she had, and how she felt about her mother. Sweet Home's cast got much bigger after season 1, with a few popular characters being killed off but multiple new ones being introduced. Among those new characters was the mysterious daughter of Yi-kyung, whose name was revealed to be Seo Yi-su. The grown-up version of the character first appeared in Sweet Home season 2, episode 4, but her origins and connections to Yi-kyung were only confirmed a couple of episodes later.

Sweet Home2's final episodes included the return of Hyun-su, who had disappeared for a year after his fight with Ui-myeong in episode 3. Hyun-su took care of Yi-kyung’s child for a few months, yet her relationship with her mother never improved. Sweet Home season 3 revised the child, whose existence was confirmed by Sweet Home villain Nam Sang-won. Yi-su could turn other people into monsters without them ever showing signs of the infection, read other people’s minds, and use special infectees as puppets, all of which made her the perfect host for Sang-won.

Yi-kyung Gives Birth To A “Cursed” Child In Sweet Home Season 2, Episode 3

Yi-kyung Was Pregnant With Nam Sang-won's Child In Season 1

Yi-kyung, the firefighter who lived in one of the Green Home apartments with her fiancé, was just about to get married when the monster outbreak began. However, Yi-kyung’s fiancé disappeared right before the first monster attacked, leaving Yi-kyung to wonder what had happened to him. Yi-kyung spent most of the season looking for her fiancé. She eventually learned that Nam Sang-won had volunteered to become one of the government’s test subjects in the research to find a vaccine or a cure for the monster infection.

Toward the end of Sweet Home season 1, Yi-kyung discovers that she is pregnant, which makes her search for Sang-won even more intense. Yi-kyung never gets to reunite with her husband, but she realizes that he knows far more about the monster outbreak than she thought. In addition, Yi-kyung’s pregnancy began to develop extremely fast, to the point it took only a few days after her first test for the child to be born. Sang-won ran into his wife while running away from the lab and, while she was unconscious, used his powers on the fetus. This is why Yi-kyung's daughter was born with special powers.

How Yi-kyung’s Daughter Grew Up So Fast

Seo Yi-su Is Actually 1 Year Old In Sweet Home

Just like Yi-kyung’s child was born far quicker than expected, the girl grew up very fast – a result of her monster powers. Yi-kyung’s daughter, who was being chased down by men who had learned of her monster powers, was shot with arrows and fell to the ground. Not only did she survive and instantly recover from the injuries, but she also went through some sort of transformation that turned a months-old newborn into a small child. Yi-su could now understand why she was being chased as well as why her mother seemed so afraid of her. This is when she begins to comprehend her powers.

Sweet Home season 2’s time jump made the show quite confusing to follow, especially because it was unclear who that child was and who were their parents. It was easy to assume that the mysterious monster child was Yi-kyung’s daughter, yet the numbers did not add up. If Yi-kyung gave birth in episode 3, the child should be one year old in episode 4, which is when the year-long time jump happens. The confirmation that the monster kid was Yi-kyung’s daughter made things way more confusing, but fortunately, Sweet Home would revisit her transformation in a flashback that cleared up things regarding the timeline.

What Powers Yi-su Has In Sweet Home

Yi-kyung's Daughter Was More Powerful Than Any Other Neohuman

Yi-kyung’s daughter is the most powerful character in Sweet Home, and she could be the key to understanding more about the monster curse. While there have been infant monsters in the show before, Yi-su is the only known character on the show to have been born as a monster. The child is not a regular human, yet she is also different from the “special infectee” or “neo-humans” referenced in the series. Whereas Song Kang's Hyun-su appeared to be the “chosen one” in Sweet Home season 1, Yi-kyung's daughter was the key to Sang-won's plans all along.

The most important power the child has is the ability to infect people just by touching them. Before season 2, there were only two known ways someone could become a monster – they would either develop the curse naturally and transform during a moment of rage or they would be bitten by a monster. However, Yi-kyung’s daughter can ignite the transformation without biting or scratching someone; all she needs to do is touch them. Additionally, Yi-su has psych powers and can hear other peoples' thoughts. Lastly, Yi-su can control people, at least the ones she has infected.

Why Seo Yi-Su Disliked Her Mother In Sweet Home

Yi-kyung's Relationship With Her Daughter Didn't Start Out Great

The relationship between Yi-kyung and her daughter was very complicated, and they were not in a good place by the end of season 2. Even though Yi-su cared enough about her mother to prevent her death by turning Yi-kyung into a monster, the girl did not care about what would happen next. Yi-kyung almost died after turning into a monster and fighting Hyun-su, but she was later made human again thanks to a new ability Song Kang's character discovered. The child has suffered a lot of prejudice and was treated as “a monster” by everyone around her, including her mother.

Yi-su had no appreciation for human life after everything she had experienced. This is why Yi-kyung wanted to keep her daughter locked and away from other people – she believed that the girl was a threat to herself and others. The child did have a positive relationship with Cha Hyun-su, who helped raise her for a few months before they went their separate ways. Yi-su's feelings toward humanity made it easier for Sang-won to manipulate her.

Why Nam Sang-won Wanted To Find His Daughter In Sweet Home Season 3

Yi-su Was The Perfect New Host For Sang-won

Nam Sang-won, the main villain of Sweet Home, knew Yi-kyung was pregnant ever since he ran into her at the lab. Having marked the fetus using his powers, Sang-won could track the child and would recognize them if they were close to him. After discovering that the child was going to be at the stadium, Sang-won and his followers went there. Sang-won’s plan worked, and he was able to identify the girl as his daughter. However, the villain was not interested in a family reunion. Sang-won’s goal was to make his daughter his new host.

Sang-won is a liquid monster who can switch bodies, which is why he has taken many identities throughout the show. The villain had been inhabiting Sang-wook’s body ever since the end of Sweet Home season 1. However, Sang-wook’s body was weakened and hurt. Additionally, the child had powers no other neohumans or special infectees had. From Sang-wook’s perspective, Yi-su was the perfect new host. Confused after the death of her mother, Yi-su ended up following Sang-won and had her body taken over by him.

What Happens To Seo Yi-su At The End Of Sweet Home

Sweet Home Season 3’s Finale Was Bittersweet

Yi-kyung died while fighting Sang-won, one of the most tragic deaths in Sweet Home. In season 3, episode 7, Sang-won took over Yi-su’s body and became more powerful than ever. The leader of the special infectees planned to turn everyone at the stadium into neohumans using Yi-su’s powers and almost succeeded at doing so. Fortunately, Eun-hyeok and Hyun-su arrived just in time to fight him. However, it was already too late to save Yi-su. Although Sang-won eventually jumped to another body, Yi-su was hurt during the fight and died in Hyun-su’s arms.

Sweet Home (2020)

TV-MA

Drama

Horror

Fantasy

Sci-Fi

Sweet Home follows the story of Hyun-soo, a reclusive high school student who moves into the Green Home apartment complex after losing his family. When a mysterious epidemic turns people into monstrous creatures, Hyun-soo and the residents of Green Home must band together to survive, confronting their inner demons and the horrifying threats outside.

Cast

Song Kang , Lee Jin-Wook , Lee Si-young , Park Gyu-young , Go Min-si , Kim Hee-jung , Kim Gook-hee , Lee Joon-woo

Release Date

December 18, 2020

Seasons

3

Streaming Service(s)

Netflix

Franchise(s)

Sweet Home