From this chapter, I have come to this conclusion:
- SungjixSumin will be ok till the end. This chap opens to solve some trust issues between them and I believe with Seju's involvement, they probably will overcome this situation and be the ultimate ending couple. And one more important point, Sungji is just a pure, innocent, cute girl, no more no less, there is no twisted personality in her. She has no hidden motive like some of us has over-analyzed :). Let's accept they should be the ending couple.
- Seju is planning sth or at least, there is sth suspicious about her. She's toooo nonchalant and it scared me a bit. For someone who's supposed to hold on tightly to Sumin, Seju's actions nowadays are very very weird. There are scenes showing that Seju's mind is not what she's showing( for example, she heard Sungji said she doesn't like them living together but acted like she didn't). And she smiles hella alot, you can see in this particular chap, she's ALWAYS smiling. Her nonchalance when accepting Sumin's rules, her smiles, I don't get good feeling about this :). But all in all, this also might the cue for her to let go. Maybe I'm just overthinking, maybe that's just a sign for the next move which is Sungji would probably accept for them to live togethet next chap (I'm 99% sure Sungji will) and Seju probably realises it's a lost so she backs away and gives the couple her blessings =)))))))).
But one thing for sure, sth is going on in Seju's head, its might be signs of her letting go or worst case, she has lost the will of continuing living and doesn't care anymore so she just accepts them all and treats this like one last time she's with Sumin :)