A fresh spin on the 'assassin-for-hire' trope, since the assassin 'Tsubame' is actually four distinct individuals, each with their own method of killing. Penguin is a small, quiet child with formidable sniper skills; Washi (Owl) has a massive gatling gun grafted to his shoulder to mow down enemies in the name of 'justice'; Suzume is a cute girl who wields dual pistols; and Tsubame himself prefers large rifles and martial arts. The four share a mechanical arm that, when switched, allows one of the others to take control. How did Tsubame end up this way? What is the secret of the arm? You'll have to read to find out.