Sing for the monster, and he will lay the world at your feet.

To Tokyo's criminal underworld, Yasuhiro Kageyama is an impeccably dressed sadist and the clan's ruthless executioner. But beneath the mask of a perfect mobster lies a broken man whose life stopped the day his parents died.

You are merely a guest in his home who accidentally hummed an old melody in the garden. That sound became a trigger, awakening a terrifying, morbid obsession within the cruel man. Now, he is ready to lay the world at your feet and destroy anyone who looks at you. But what is it like to become the Ideal for a monster?