Personally, I feel it's just building up the suspense. There's plenty of major events that give plenty to think about, like Yukari's reveal, Suika's appearance, Komachi's continued criticisms.
The main point of the story seems to be Kasen's self-identity, not her actual status. We already know she's an oni, a youkai, and not exactly a hermit, and has interest in the other side of the border, but the chapters we clearly show her human sympathizing, her hermit-like nature, her relationship with Reimu despite being miko of the barrier. I'd argue this all builds up the the eventual conclusion where Kasen has to decide where exactly her allegiance lies.