One line or two more about Sungji being perceptive, please, I really don't remember anything about it at all.
at the very beginning, she was able to know that Sumin was living alone,
She said she saw the electricity's invoices, water supply's invoices, etc, were sent to Sumin's workplace, that's the reason why she got that idea. But really, all of those things from my house were always sent to my father's shop, my father was not living alone in our house. When I moved to live with my brother, all of the invoices from his house were also sent to my brother's workplace, not the house. Using Sungji's perception, you would guess that my farther and my brother are living alone, which is false.
ch24, she got immediately that Sumin lacks frankness
Sumin hasn't been honest with her since the beginning, not to mention she almost got eaten alive by Sumin several times, yet she just found out about Sumin lacking of frankness in chapter 24.
again, bed talk in ch 46..
If you were talking about when Sungji was asking if she could ask Sumin everything, then Sumin paused a bit, and she then realized that Sumin couldn't agree with that. I personally think you don't necessarily need to be perceptive to read that kind of situation.
ch51conversation..
She said Sumin had given her her heart, yet in the chapter where she caught Sumin cheating, she said Sumin was always ready to leave her. That was a huge contradiction, wasn't it? Did she really ever understand Sumin?
was able to remember Seju's house code before she knew she would need it
She went back to Seju house again to bring Seju some medicines because Seju didn't have those in her house. There's no way she could know that she would need Seju's house password later since she couldn't possibly know about Seju having no medicine before entering the house and asking Seju if she had some.
then later, ch55 she kinda knew that Sumin was uneasy.
I'm not sure what happened in chapter 55.