Saiga is a normal high school student with a gift in mathematics. His daily routine is disrupted when his family gets news that his Father's remains have been discovered—a noted archeologist and researcher who had gone missing while exploring a site many years before. Among his remains were notes and artifacts that needed to be identified by the family near a notable triangular mountain in Japan known as Japan's pyramid, a place suspected by some to be man-made. A meteor containing a strange robotic lifeform falls from the sky and begins to cause destruction, putting Saiga in danger and causing a mysterious bracelet from his father's research to activate and merge him with an ancient robot burried within the pyramid—a robot the runes describe as Reideen. It is now up to Saiga and guardian Reideen to fight against this unknown alien threat from the sky. (Source: ANN)

The year is 2050. A young engineer named Derrida Yvain became famous thanks to his contribution to the development of the Autonomous Machine DZ at Rebuild, the manufacturing company founded by his father. One day, Derrida and his colleague Nathan discover a flaw in the DZs and try to warn their boss, but are ignored. Although Derrida and Nathan are aware of the danger, they reluctantly decide to put off taking any measures, and instead go to Nathan's daughter Mage's birthday party. The next day, after enjoying a peaceful day, Derrida and Nathan are suddenly attacked by unknown forces. At the end of the escape, Derrida falls into a cold sleep machine and 10 years later, he wakes up to a devastated world in the middle of a war. While Derrida is attacked by a group of out of control DZs, he almost gives up, but he recalls Nathan's last words. Take care of Mage. Despite the harsh fate that has fallen upon him, Derrida sets off to seek Mage. (Source: ANN)

As the united world fights for its freedom against the alien forces known as the Neuroi, human girls with magical abilities—called witches—continue to battle. With the persisting conflict affecting morale, Grace Maitland Steward, a retired witch who still serves in the army, presents a plan advocating the power of music as an invaluable support that can change the tides of war. Unfortunately, her proposal is written off, prompting Grace to find a way to prove the potential of her idea to her superiors. She enlists the help of Aila Paivikki Linnamaa and Eleonore Giovanna Gassion—two witches who have already seen some success as singers—to recruit other witches and form the League of Nations Air Force's Music Squadron. The campaign manages to produce seven promising candidates. Among them, 14-year-old Virginia Robertson, despite having no military experience whatsoever, seems to possess an ability too significant to ignore.

In the near future when technology has significantly advanced, a famous AI TV fortune teller seemingly foresees high school student Asahi Kashiwagi's day with pinpoint accuracy. On his way to school, he encounters Aoi Izumisawa, Bai Mongfa, Karin Istel, Amelia Irving, and Ilya Ilyukhin. Despite meeting them for the first time, Asahi suddenly receives love confessions from all of them at the end of the same day, perfectly aligning with the fortune teller's prediction. As if that was not enough, Asahi soon learns that these five individuals are actually candidates to become his bride, and they have been invited by his father to live at Asahi's home. Left with no other choice, he reluctantly allows them to stay, resulting in a bawdy turn of events that brightens up his average high school life. However, as Asahi spends more time with them, forgotten memories gradually resurface. While uncovering the hidden truth, Asahi begins to believe that his fate with these potential partners might be more than just mere coincidence.