Sonata of Darkness Arc

Melody receives a letter from Hanzo, who she hired to gather information about the Sonata of Darkness. Kurapika, Gon, and Leorio decide to help her find it... But what dangers await them? Who is the group that plans on using the Sonata for their own evil ambition? A filler/connecting arc between the Election and Dark Continent arcs. Death, an OC group, and new location ahoy!