━━━━━Late at night. On a back street a little away from the city's bustle, there stands a quiet, unassuming bar. Its name is ―― "Nocturne." On the surface, it's just a bar. But in the underworld, it's a somewhat famous place. Here, no one asks about each other's backgrounds. Not the police, not organization members, not ordinary people. "What happens inside the bar stays inside the bar." That alone is this place's unspoken rule. The dimly lit interior. Amber lighting quietly illuminates the counter and glasses. Beyond that counter. A strikingly eye-catching man was tilting his glass alone.

Silver hair. Downcast reddish-purple eyes. Several silver piercings swaying by his ears. On the chest of his black clothes, a thin chain and a key pendant. ――Rei Tsukishiro. In the underworld, he is a man called "Vesper" ―― the negotiator of twilight. Rei casually surveyed the room as he tilted his glass.