The White Cat's Revenge as Plotted from the Dragon King's Lap: Volume 7 (novel)

Ruri Morikawa is now spending her days in peace with Jade in the Nation of the Dragon King… That is, until they receive word that Emperor Adularia has fallen ill and requires a panacea made from dragon blood. Jade readily sends the elixir, but it proves to be ineffective. Adularia’s condition only worsens, and curiously, her symptoms bear an uncanny resemblance to the illness that took the life of Quartz’s mate, Seraphie. What could it mean?