Mikio Sakai, 酒井ミキオ Dive in the Sky Lyrics belongs to the anime Planetes, take a look at the argument:
Thor and Rai Klein, 11 years old, are sent away from their home planet after their parents are murdered. They awaken on Chimaera, a terraformed planet where carnivorous plants predominate and the few humans who live there are divided into four "Rings." They meet a young man named Zagi shortly after, and the twins learn that only the "Jyu Oh Sei"—the one who conquers these four Rings—is permitted to leave the planet. Thor resolves to survive in Chimaera's harsh, merciless environment, driven by his desire to return home and learn the truth about his parents' deaths. However, he quickly discovers that there is more to this strange ecosystem than meets the eye. As Thor becomes entangled in the politics of the Rings, he learns more about his parents' murder and, ultimately, humanity's fate.