Well, finally got around to reading the latest chapter. I hope to hell Sumin pushes Seju away and doesn't give into her whims and have sex with her.. I like Seju but she's so incredibly single-minded and selfish when it comes to Sumin, I hope Sumin realizes doing something with Seju now would just damage her relationship with Sungji (guilt, finding out, etc) and then she'd be back at square one and unhappy.
There was never any doubt in my mind Sumin had lingering feelings for Seju, but their relationship was so unhealthy that I really can't imagine any possible way for them to fix it.. I want Seju to be happy as well, and the only way that will happen is if she's able to move on like Sumin is trying to.