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

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.