*contains spoilers from episode 7*
In the latest episode of “Twenty Five Twenty One,” Na Hee Do (portrayed by Kim Tae Ri), found a recorded—a what seems to be intimate—conversation between Baek Yi Jin (portrayed by Nam Joo Hyuk) and a certain Da Eun.
Now, the question every viewer is asking now: Who is Da Eun?
Well, some say it might be Kim Hye Yoon or Choi Hee Jin (both from “Snowdrop”), but eagle-eyed netizens were able to get a clearer look at Da Eun and Yi Jin’s photobooth photo and even saw an actress post about the scene via her Instagram account.

Hence, they’ve connected the dots and realized that might be “Blue Birthday” actress Kim Yi Seo. The actress started in “Mine,” “Live On,” and “Designated Survivor: 60 Days.”

What do you think? Do you think they’ve found Da Eun? What are your theories?
UPDATE AFTER EPISODE 6
What we know so far is that the girl in the photo with Yi Jin is different from Da Eun. The girl in the photo is Min Young, also Yi Jin’s ex-girlfriend.
UPDATE AFTER THE ENDING
At the end of the series, Da Eun was only mentioned one more time (when Hee Do and Yi Jin were casually fighting.) Her identity was never confirmed.
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the sticker photograph is not Da-eun, Ko Yurim tell them that the girl in photograph is different person named Min young
Yup! This was added at the end of the article as an update from episode 6. 🙂