Shinki are miniature female mecha, built and put through combat trials inside an isolated facility. One of them, an Arnval Mk. 2, disobeys her orders and escapes the battlefield. Tsubasa, who shares the local boys' ambition of becoming a Shinki Master, comes across the damaged android, brings her back online and names her Kaguya after the Moon Princess. Her maker is far from happy about her defiance and dispatches another strong, brutal Shinki to track her down. Meanwhile, Tsubasa is set on winning his first Shinki battle with Kaguya at his side. The ten-episode sci-fi mecha action ONA is an original story built on Konami's Busou Shinki line of armed female action figures, and it follows Tsubasa's coming of age alongside the fights.