The Condemned Villainess Goes Back in Time and Aims to Become the Ultimate Villain (Light Novel) Vol. 9

As part of their vacation, Claudia and Sylvester attend an international conference together. The countries' future leaders assemble in an impregnable fortress on a remote island, assured of its security--until the banquet begins, and some attendees vanish without a trace! During the ensuing investigation, our heroine is joined by an eastern prince known for his philandering ways. Their efforts to solve the mystery soon evolve into a search for treasure rumored to be hidden within the ancient halls!