All the Signs Yi-Jin Is Min-Chae's Father on "Twenty-Five Twenty-One"

Min-Chae is a Kim and Yi-Jin is a Baek, which indicates that the two are not father and daughter. But is this meant to throw us off? Twitter users have long speculated that Yi-Jin could have changed his name. We've seen how the impact of his father's bankruptcy has followed Yi-Jin wherever he goes, and it's possible he changes his name to Kim because of this. But developments in episode 10 may suggest Yi-Jin changes his family name to Kim (and maybe even his first name as well) because it's his biological name.

In episode 10, Yi-Jin's father calls him after a hard day at work and consoles him by telling him he was "his greatest consolation 10 years ago and you still are today." Yi-Jin responds by saying, "Thank you for raising me to be who I am." Yi-Jin is 21 years old in episode 10, so his father's dialogue hints at the possibility that he was adopted at 13 years old (why else would he have been his consolation 10 years ago instead of 21 years ago?). It may also explain Yi-Jin's general hard-working and humble personality in the face of hardship despite the fact that he was seemingly raised with a silver spoon in his mouth.

If Yi-Jin is, in fact, adopted and he decides at some point to change his name to his birth name, this could explain why Min-Chae never recognizes his name as Baek Yi-Jin. It also adds another layer to the moment when Jae-Kyung asks Min-Chae if she "knows" Yi-Jin in episode four. She may have been asking if Min-Chae "knows" her dad's name was once Yi-Jin.

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.

In episode four, present-day Hee-Do's mother mentions seeing Yi-Jin a month prior. Hee-Do looks somewhat distressed about this, which may indicate she still cares about Yi-Jin or that they didn't end on the best terms. Some fans are interpreting this as an indication they parted ways long ago on bad terms (otherwise, mentioning seeing Yi-Jin a month ago wouldn't have caused Hee-Do's expression to darken). But Hee-Do has a happy disposition when looking at the old photos of her friends (including Yi-Jin), so it could also suggest her expression darkens because of something else.

Later, in episode 10, Min-Chae mentions the trip Hee-Do went on with her high school friends, and Hee-Do says she doesn't remember the trip at all — despite expressing that she hoped the trip would last forever while they were on it. This, again, brings into question what type of lingering feelings Hee-Do has for Yi-Jin. While the fact that she's forgotten about a seemingly meaningful experience with Yi-Jin could suggest they didn't end up together and he's not Min-Chae's father, it could also mean that they did end up together and simply had 15 additional years of memories together that replaced their first trip to the beach together.

In the later episodes of "Twenty-Five Twenty-One," we're given glimpses of the decorations in Min-Chae's room. Twitter user @ImZeroOclock pointed out the decorations include a bike and telescope figurine. Throughout the series, we learn that Yi-Jin once dreamed of joining NASA before he was forced to drop out of college because of the IMF crisis. He also rode a bike to deliver newspapers when he first met Hee-Do as a part-timer. Of course, there's a possibility Hee-Do picked out these decorations, but there's also a possibility Yi-Jin gave Min-Chae the decorations.

A theory that could give insight into present-day Hee-Do's distressed expression when her mother says she saw Yi-Jin a month ago in episode four is taking hold on Twitter. When mentioning that she saw Yi-Jin, Hee-Do's mother states his full name, which could suggest she is not familiar with him. Twitter user @taeri_yeosin theorized that Hee-Do's mother may have dementia, so she does not remember that Yi-Jin is now her son-in-law. Rather than being about any dark memories about parting on bad terms, Hee-Do's negative reaction could be because she is upset her mother does not remember seeing him more recently, or that she thinks she saw him last month (Min-Chae's father travels for work and hasn't been back in quite some time because of COVID, so perhaps there was no way Jae-Kyung saw him a month ago).

This theory also goes well with the theory that Yi-Jin changed his name and would explain why she uses an old name rather than his new one. This would also explain why the women avoid talking about Yi-Jin, as it would confuse Jae-Kyung.

In episode 10, present-day Hee-Do drives Min-Chae to the hospital to get her bruise checked out in a red car reminiscent of Yi-Jin's red convertible, where he and Hee-Do shared many of their relationship-defining moments. Could the red car be a hint that Yi-Jin is still part of Hee-Do and Min-Chae's lives?

When they return from their group trip to the beach in episode 11, Ji-Woong tells everyone to put their names down on photos they want him to print for them from the day. Yi-Jin was the only person who put his name on the solo photo of Hee-Do looking quirky on the beach in her red-stripe T-shirt, and Ji-Woong delivers the photo to Yi-Jin's office personally in episode 12. Yi-Jin ends up using it as a bookmark. Eagle-eyed viewers noticed that very picture ends up in one of present-day Hee-Do's photo albums. If Yi-Jin was the only one who asked for that photo and it's now in present-day Hee-Do's photo album, it could suggest the pair ended up together and consolidated their memories into one photo album.

In episode 12, when everyone gathers at Yi-Jin's apartment to say their goodbyes before the world possibly ends because of the Y2K bug, Yi-Jin's white cassette player can be seen behind Ji-Woong. Fans noticed that the cassette player can be seen among Hee-Do's belongings in the present day. They know it's not Hee-Do's because Hee-Do had a black cassette player. This discovery, along with the photos Hee-Do has and the decorations in Min-Chae's room, further suggest that Yi-Jin and Hee-Do are together in present day and Yi-Jin is Min-Chae's father.