Season synopsis
Contains spoilers for this season and earlier seasons.
In 1609, an alien named Do Min-joon stays on Earth after rescuing Seo Yi-hwa and missing his chance to leave. Four centuries later, he is a university professor with only months before his long-awaited departure when celebrated actress Cheon Song-yi moves in next door. Her career collapses after fellow actress Han Yoo-ra dies and suspicion turns toward Song-yi. Min-joon uses his legal knowledge and concealed powers to help protect her, even as he tries to keep their growing attachment at a distance.
Song-yi learns that Min-joon is not human, but his insistence that he feels nothing for her briefly drives them apart. The danger around Yoo-ra’s death is tied to Lee Jae-kyung, the older brother of Song-yi’s longtime friend Lee Hee-kyung; Jae-kyung threatens witnesses and targets Song-yi as she becomes a liability. Min-joon’s attempts to shield her bring his secret closer to the police, while his powers grow less reliable as his departure approaches. Jae-kyung’s father refuses to help him escape imprisonment. Song-yi’s family and former rival Yoo Se-mi also help keep her safe.
In the final week, Min-joon’s health falters and he and Song-yi share an ordinary stretch of time before he disappears during a meteor shower. She grieves, returns to acting, and keeps looking for him. Three years later he reappears at an awards ceremony, where time stops and they kiss before he vanishes again. He explains that a wormhole sent him away and repeated trips now let him stay longer, though not permanently: his latest visit has lasted a year and two months. The episode’s final epilogue shows him reappearing beside Song-yi as she sleeps, saying he is home and embracing her.