Ten years after the murder of pop idol Ai Hoshino, her young (and unusually mature) twins are now poised to enter high school.

While her death has had a profound effect on the children, it's manifested in polar-opposite ways. Ruby is determined to follow in her mother's footsteps and become an idol, but Aqua has no desire to stand in the spotlight.

Instead, he works behind the scenes in the entertainment industry, all while harbouring an ulterior motive: discover the identity of the accomplice in his mother's untimely death!