Finally sort of addresses the marital violence against women casually accepted in a lot of the previous stories. A woman tries to use Ho-Yeon and Baek-On to take out her abusive husband. A man discovers that his celestial wife has a more earthly origin. (I wish the translation weren't "angel" -- it's culturally specific for the wrong culture.) Baek-On brings disaster to the harmless and finally notices it, and asks Master Son for advice; she tells him the story of how she met his father, with uneasy implications for exorcism and coexistence of spirits and humans.
There's a prologue about two warring generals which is strangely unresolved, unless it's meant as thematic foreshadowing for the first story. We also don't get more about Baek-On's personal backstory after the intriguing hints at the end of Volume 4; I'm hoping Volume 6 will follow up.
I am now convinced Baek-On's father totally had a thing going with Bi-Ui the foxy dancer lady on the side and that SeUl is Baek-On's half-sister. Your fanon may vary.