*Spoiler*
Dongtae and Eunju will never be coupled.
Dongtae has mixed feelings for Eunju as of Season 3, but in Season 4 and a couple episodes before that they are acquaintances and allies (yes, I read the Korean counterpart). They never get together. IN Season 4 Dongtae and Mio are dating and are together, but Dongtae still appears to have emotions for Eunju.