Small for his age, Yukinari has been bullied and abused by girls all his life. Now in high school, he has developed a rare condition: whenever girls touch him, or even come close, he breaks out in hives. Imagine his surprise, when he is suddenly transported to the city of Seiren on a mystic world invisibly orbiting the Earth, and populated with vast numbers of women and very few men. Fortunately, he has a new friend, Miharu-chan, whose touch inexplicably doesn't affect him.

In the year 2061 AD, Japan has lost its sovereignty. The Japanese people spend their days as oppressed citizens after being divided and ruled by the four major trade factions. The country became the forefront of the world following the deployment of AMAIM—a humanoid special mobile weapon—by each economic bloc. One day, Amou Shiiba, a boy who loves machines, meets Gai, an autonomous thinking A.I. The encounter leads Amou to cast himself into the battle to reclaim Japan, piloting the AMAIM Kenbu that he built himself.

Once upon a time, an unidentified enemy, the Unknown, suddenly appeared. The "Super Evolutionary Railway Development Agency," had developed the "Shinkalion," a robot that transforms into a bullet train, as a countermeasure against this threat.

The official website for the Nanbaka television anime announced that the "Nanfes" event in April will screen a previously unreleased anime special.