Ryo Saeba is a sniper and private eye ("sweeper") based in Tokyo's Shinjuku Ward, who possesses unrivaled marksmanship and an over-the-top obsession for the opposite sex. He and his partner Kaori Makimura serve as bodyguards and perform other duties for his clients. Their latest client is Ai Shindo, a model who's being attacked by mysterious people and unknowingly holds the key to a vast city-wide conspiracy.