Three hundred years ago, Shen Zhaoyun led a team to build the alliance's first combat mecha, honored by later generations as the "Mecha Ancestor." Three hundred years later, she accidentally is reborn as a freshman in the alliance's first academy with level D physical fitness, so poor she cannot even afford a mecha. Facing a mecha era that has long turned upside down, she simultaneously relearns modern technology while repairing mechas, fighting matches, selling systems, building clubs, and conducting research. As the first-generation Zero is recognized again and lost research materials gradually emerge, she also begins to discover that her death, her former comrades, and three hundred years of mecha development seem to hide unknown secrets.