well, Sumin inner thought was:
" I'm miserable about the fact that I'm scared of this emotion" ..
of course she would not open up that easily .. Sungji knows that, and respects it. if you read ch41 dialogue, and again the bed talk in ch46.. she asks Sumin if she could really ask about anything..
being comfortable and in love with someone does not necessarily mean she would open up to Sungji.. even Nammi does not know very much about wt happened neither does Summin think about it.. she pretend all that did not happen
and thus later in ch 50 admits to herself that she still have feelings for Seju
only after Sungji caught them, Sumin said that her situation with Seju is not just friendship.. finally she told Sungji that.. (it seemed all characters told her about Sumin x Seju except Sumin herself hehehe)
will we see Sumin open up more? .. that girl avoided dealing with her emotions with Seju for 10 years.. unless something major happened, she would just keep it to herself. if Sungji tries to push Sumin more for opening up, it will only cause Sumin to feel uneasy and even more defensive.
last edited at Mar 9, 2017 10:19AM