Youtuber Drama Hyung theorized that it's possible Yi-Jin leaves Korea to follow his dreams of becoming a renowned international reporter (when he's 25 and Hee-Do's 21), only for Hee-Do to find out afterward that she's pregnant with Min-Chae. He theorizes that she decides to keep it a secret from him so he can continue to pursue his dream, drawing attention to a scene in episode six in which Yi-Jin introduces a visiting Australian fencing referee to a new restaurant and the two discuss seeing someone working with a baby on their back in a carrier. The Youtuber believes this foreshadows the future of Hee-Do putting parenting duties on her back as a single mother. But this future would require Hee-Do to not only marry someone else who adopts Min-Chae, but also to lie to Yi-Jin about the existence of their biological daughter for nearly 15 years, which feels unlikely.
Perhaps more believable is the idea that present-day Yi-Jin is, in fact, an international reporter and Min-Chae's father who travels abroad a lot. In episode seven, Min-Chae receives a ballet dress from her father, and Hee-Do indicates that if he traveled back to Korea amid the COVID pandemic, he'd have to quarantine for two weeks entering the country, as well as when he travels abroad again. We already know Yi-Jin wants to be a reporter, so being an international reporter doesn't seem like too much of a stretch for him, especially considering he's fluent in multiple languages. It's possible that he is Min-Chae's father and married to Hee-Do and that we simply haven't seen him because of his work abroad.
