volume 1:It began in 1945, at the end of the Pacific War. Alien invaders filled the Earth skies, and mankind was forced to confront an unprecedented threat. For the first time in human history, people of all cultures came together under one banner. This war has now been raging for over fifty years. Countless lives have been lost, and the Japanese military is now forced to rely on young people such as Atsushi Hayami and his high school class, also known as Unit 5121. This new generation fearlessly struggles on with the aid of the HWT humanoid combat machines and the devastating PBE bomb. volume 2:The war has claimed the lives of far too many to ever be avenged. Each death leaves a vicious unseen wound upon the surviving combatants. Unit 5121 will discover that no group is immune to this syndrome. Their next mission will leave them outgunned, outnumbered and one member short. Danger, fear, and loss will tear at Unit 5121 in ways that their young minds could have never imagined. There is no time to mourn in the heat of battle. Can this team stand fast or will combat fatigue wear them down?volume 3:The Genjyu step up their campaign of destruction as the dawn of the new millennium approaches. Tanabe is promoted to PBE supervisor, one of the most dangerous assignments in Unit 5121. Hayami and Mai find themselves in the spotlight when the news media takes an interest in Unit 5121's war against the alien menace. Things take an abrupt change when another HWT unit requests Mai as a replacement pilot. Hayami has until the clock strikes twelve to admit his feelings for her, or she'll be transferred out of his reach. In this war, it could mean forever.