Mark of the Firefly (Tsukkiyama)

Nothing much of interest ever happens in Yamaguchi's little scrap town on the outskirts of the habitable continent. Just scavenging and sales. So, when his long-time friend, Kageyama, bursts through Yamaguchi's door in a panic brandishing a magnificent object branded with the Mark of the Firefly, a wealthy neighboring empire, he doesn't have much of a choice but to leave town. Breaking onto a continental freight train, getting caught and rescued multiple times, and becoming one of the main players in a continent-wide game of espionage and royalty was not exactly on Yamaguchi's to-do list, but what other choice does he have?