Mile, Pauline, Reina, and Mavis face off against the chief of the elder dragons in a battle that will test the limits of their power. It's up to the Crimson Vow to decide whether war breaks out between dragonkind and humans. But even if the girls emerge unscathed, there's war of another kind on the horizon--a war between the Crimson Vow and the Wonder Trio, over Mile!
So, we got to see characters from the first three volumes again. That was cool. Also, this volume added greatly to the overall coherence of the series. Things all start to get tied together. There's even hints of some plot conflicts being resolved. Though of course, it's played for laughs. I'll keep on following the series and maybe watch the anime.