In the third season of Sweet Home, Lee Eun-hyeok, played by Lee Do-hyun, returns neither as a human nor as a monster.
Eun-yu’s brother, Lee Eun-hyeok, became the leader of the residents of Green Home during the monsterization outbreak in the first season.
At the end of the season, Eun-hyeok did not leave Green Home with the other residents, as he showed symptoms of monsterization.
He had promised Eun-yu that he would return to her, so throughout the second season, Eun-yu keeps searching for him.
She finally reunites with her brother in the third season, but their meeting is nothing like what Eun-yu imagined, as her brother is no longer the person she once knew.
Eun-hyeok’s return as a neohuman
Eun-hyeok turned into a monster but later reverted to resembling his human self. He looks human, but he is neither fully human nor a monster.
Eun-hyeok became a neohuman, the final stage of monsterization. Neohumans are born out of cocoons called the heart and, upon death, return to the heart to be reborn.
Eun-hyeok emerges from a cocoon but is attacked by Sang-won, who aims to kill all neohumans. This is when Sergeant Kim finds Eun-hyeok.
During his escape from the Bamseom Bureau, Sergeant Kim takes Eun-hyeok along. Eun-hyeok then takes his own life to return to the heart.
Eun-hyeok is reborn again without any prior injuries. Following his rebirth, he accompanies Sergeant Kim to the stadium, hoping to kill Sang-won.
Reuniting with Hyun-su and Eun-yu
On their way to the stadium, Eun-hyeok encounters Hyun-su and Eun-yu. He remembers his sister but does not bother approaching or talking to her.
As a neohuman, Eun-hyeok lacks emotions. He feels nothing towards Eun-yu and only wants to work with Hyun-su because he can be useful to him, unlike Eun-yu.
However, Eun-yu refuses to give up on her relationship with her brother. She believes that he can be taught to feel again, knowing that neohumans are fast learners.
Eun-yu tries to remind him of their past memories, but before she can evoke any feelings, she begins undergoing monsterization and parts ways with her brother and Hyun-su.
Eun-hyeok continues with his plan of going to the stadium with Hyun-su to face Sang-won, who has taken over Yi-su’s body.
While Hyun-su is unwilling to harm Yi-su’s body to kill Sang-won, Eun-hyeok has no such reservations and ends up killing Yi-su despite Hyun-su’s efforts to save her.
Even her death does not affect Eun-hyeok, and he feels no remorse, as he considers Yi-su’s death a necessary sacrifice.
He also offers to sacrifice himself to kill Sang-won, knowing that he will be reborn. Ultimately, it is Sang-wook who kills Sang-won, sparing Eun-hyeok from sacrificing himself.
Eun-hyeok and Hyun-su then go their separate ways, but not before Hyun-su tells Eun-hyeok that he intends to reunite him with his sister.
As Eun-yu had asked, Eun-hyeok begins learning to feel emotions again. The family picture he still keeps close serves as his guide.
In the end, he is seen living at Sweet Home, the new shelter for humans and neohumans, with Hyun-su and Eun-yu, making efforts to reconnect with his emotions.
