Assassins--they are humans that have exceptional skills which they use in killing people. The most dangerous among them is the Assassin of Crimson--the former leader of the Assassin guild Yuuyami, and the one who killed the country's leader, King Mars. Due to this, the country's princess has declared that whoever captures her will obtain fortune and become the princess' husband, essentially becoming the next king.

Virgil is a guy who has red hair and looks like a girl. He is travelling with a performing troupe while searching for his twin brother Serge. His peculiar features seem to have matched the known characteristics of the Assassin of Crimson. The following events will lead him to discover the mystery behind the death of the king--and the identity of the Assassin of Crimson.