It all seemed like another regular day for the photojournalist Wakatsuki Tetsuya when something big happened. ALIEN INVASION! This brings his journalist's blood to a boil and he goes to check it out. It is there he meets, standing in a pool of blood and corpses, the alien girl Kahm, who looks exactly like a human if you take away the pair of horns growing from the sides of her head. There they fight and Tetsuya wins and takes her sword. Kahm retreats but soon comes back to retreave the sword and save Tetsuya from Japan's unavoidable fate….being wiped off the face of the earth! On her spaceship, Tetsuya learns that Kahm is not only a princess but also the heir to the thrown of the Santovanku Empire! Well, one comidic fight leads to another and now Tetsuya and Kahm are on their way to Kahm's father to declare their marriage?!

Links:

• Author's Twitter
• OAV on ANN