Harima Sakura is a Picodroid of the G4 type, a living being able to learn on her own and evolve. She can shrink herself small enough to enter the Pico Universe, the realm of atoms that the human eye cannot see. With very strong athletic ability and a firm sense of justice, Sakura works alongside a range of researchers and scientists to investigate what lies inside atoms. The single-episode music and science fiction ONA was made by the Japanese research facility SACLA to promote its X-ray Free Electron Laser, which it describes as the brightest source of x-rays in the world.