I really like the way the author write about the relationship between Kyoko and Rei.
They have a complicated and toxic relationship, in which Kyoko constantly attacks and blames Rei for her own trauma and sadness yet unable to understand or sympathy or feeling guilty for Rei, a child who have to suffer from trauma from childhood and depression in his teen.
However at some point, I feel like they really look like siblings. Kyoko always shows how much she hates him, but his place is the only one she can feel secure, as in society, she is not only have to struggle with her trauma, but also the dilenma of loving a married man. They can be a very loving siblings, but completely at the current chapter.