Tokyo Underground, Vol. 3: The Promise
After becoming Ruri's bodyguard, Shiel, Master of Thunder, develops sympathy for Ruri- especially after she overhears Pairon's plot to resurrect the hideous dragons in exchange for Ruri's life!  Shiel helps Ruri escape confinement and tries to help her reunite with Rumina, but Pairon intercepts them and demands a duel to the death.  While they promise each other to stay alive can either Ruri or Shiel keep that promise?