Obstetrician-gynecologist Gorou Amamiya is tasked with helping deliver the children of Ai Hoshino, a famous pop idol whom he admires, without the knowledge of the general public. However, on the night of Ai's delivery, Gorou is murdered by an obsessive fan of Ai's and is reincarnated as Aquamarine "Aqua" Hoshino, Ai's son, retaining his memories of his previous life. Unbeknownst to him, Aqua's fraternal twin sister, Ruby Hoshino, is the reincarnation of Sarina Tendōji, one of Gorou's patients who was a fan of Ai's. Four years later, Ai is murdered by the same fan who had killed Gorou. The fan later commits suicide, but Aqua deduces that the murderer may have had his and Ruby's father as an accomplice and resolves to infiltrate the entertainment industry to find and kill him.