About 100 years ago. In order to seek the life energy "Abit" that was exhausted in the mother planet, mechanical life forms came from another dimension. In order to shuttle through dimensions, they shrunk their posture to the shape of arms, landed on the earth rich in "Abit", and were able to live on the earth by parasitizing other creatures. They secretly contacted some humans and began to look for "Abit". People called them "mechanical arms" in that form. Time has come to modern times. A cube with a "mechanical arm" sealed in it was lost from the research facility of the large enterprise "Mirror Group". An ordinary middle school student, Guang, who accidentally discovered it, unlocked the seal of the cube. From there appeared Alma, a "mechanical arm" that had been dormant for 100 years. Alma wanted to parasitize on Guang's body... Guang and Alma's wonderful life together began unexpectedly.