"The Dark Oath" is the second in the series of novels that make up "The Diasminion Chronicles". People who are not familiar with "Encircle the Sun" may find the story a bit hard to follow, so I'd recommend reading that novel first.

Our story follows Hironah, the daughter of Champions Keisuke and Ayame, as she tries to make sense of the happenings in her changing world. 25 years have passed since the Champions returned home after completing their Task. The country has changed drastically under the rule of Harata, now the Emperor, and his Empress Kat, former Champion of Clan Empirian. Boundaries between the Clans are collapsing, and the former policies of order and surveillance have been replaced by The New Law. While many of Diasminion's citizens enjoy their newfound freedoms, the new order is not without its perils...