《机动战士高达 THE ORIGIN》系列的第6作。继续讲述了因父亡故而变成孤儿的卡斯巴尔与阿尔黛西亚,在动荡大时代的洪流之中,面临的又一场人生巨变……标题中的“赤色彗星”便是夏亚·阿兹纳布尔的称号。由于夏亚的机体无论是扎古、大魔,还是后来的沙扎比等都是红色的,夏亚操纵 这些机体风骚地驰骋在战场上,故被敌人称作“赤色彗星”。
After the Dawn Rebellion, Char travels to Earth and meets a girl with mysterious powers named Lalah Sune.
Meanwhile, Amuro's father Tem Ray is working on the RX-78 development project. Learning of the defection of Doctor Minovsky, a key figure in Zeon mobile suit development, he heads for the moon. History's first battle between mobile suits unfolds in the twilight zone of the lunar surface.
Then comes Universal Century 0079. Side 3, the space city furthest from the Earth, launches a war of independence against the Earth Federation government under the name of the Principality of Zeon.
An era of violent upheaval begins, in which half of the total human population will be killed...