Spoiler
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I don't think that was the face NK made. It's just how the redhead saw it because he again was allowed to enter Yoon's residence and spy on him doing with NK. Seriously, Yoon needs to rethink his security. It's a wonder he's not been assassinated in his sleep by now. People just go and out of there.
lmao I was thinking the same thing. It seems like his only "guard" is the old servant. Even without Jiwha interfering he was bound to be attacked some time. And to think his little brother has so many guards around him. That makes me even more curious about SH's past because logically, both of them should be protected and perhaps SH even more because he's the oldest.
And the way they are shown make Seungho especially meek/whipped, with a Na-kyum towering above and that victorious smile, and a Seungho that seems to have placed his forehead by Na-kyum's chest. Although they are more intimate this time around, they're not at that stage (yet? :) ).
To me, Jihwa picturing them like this is part his jealousy-fulled imagination, part his ''friend'' building him up, easily manipulating him at his lowest with a very dangerous ''advice''.
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Holy shit that smile, wtf Nakyum lol
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Oh god, can't wait to know the whole story and translation