Today, as the invasion war by extraterrestrials comes to an end, the hero Shibusaki Takashi retires from the military and returns to Japan. After escaping from days spent on the brink of death, the normal high school life he had long dreamed of finally begins… filled with anticipation, Takashi looks forward to it. However, in reality, his daily life is turned upside down by a group of unique and beautiful girls, including his comrade from Northern Europe, Natalie, and he finds himself caught up in unexpected battles every day! Has his life stopped being normal because he himself has changed...？