In 1967, humanity discovers a hostile alien race called the BETA on the Moon. Despite their attempts to stop them, the BETA makes landfall on Earth in 1973, which leads to a long, grueling 30-year war where the BETA conquers half the Eurasian continent while humanity can only stall them. In 1998, Yui Takamura is a student of the Kyoto Royal Guard Academy where she studies to become an Imperial Guard TSF pilot along with her friends Aki Iwami, Izumi Noto, Shimako Kai and her rival turn friend Kazusa Yamashiro. As the Asian front lines turn dire, Yui's uncle Eiji Iwaya meets with Yuuhi Koubuin of the Shogunate family over a new weapon that might help turn the tide against the BETA. As Yui and her friends improve themselves in TSF combat training, the Korea peninsula is overrun by the BETA. As the Korean front falls and the BETA invades the Japanese isles, Yui and her fellow cadets are ordered to assist the Japanese army in defending the capital of Kyoto.