The Great Invasion

(from ebookjapan):
One day, a person claiming to be an emissary from the Kingdom of Tasmania announced a declaration of war against the United States and recommended unconditional surrender. The U.S. government did not take the message seriously, but as predicted by the messenger, an atomic bomb exploded at a nuclear test site in Nevada. ......? (The Great Invasion) Suddenly, the human race comes to an end. Hikaru and Yoko, who are in love with each other, are approached by a strange bubble, but what exactly is it ......? (The Century of the Fetus) This collection of four short stories also includes "The Mother," written by Sakyo Komatsu.