April 10th. Yesterday marked the final day of spring break, meaning today began as a school day. After being roused by his adorable younger sister, Itsuka Shidou assumed it would be just another ordinary day. As for foreseeing the chance encounter with the girl who claimed to be a spirit... Accompanied by a sudden shockwave, the cityscape disappeared without a trace. In a corner of the street, now transformed into a crater, the girl stood there. "—You, have you come to kill me too?" She is the calamity that will wipe out humanity, a monster of unknown origin, and a being rejected by the world. There are only two methods to stop this girl: annihilation, and conversation. His younger sister Kotori, clad in a military uniform, thus told Shidou: "Since it's like this, just go date her, and make the spirit fall for you!" "Wh.. whaaaaaaaat!?" Enter a new age of boy meets girl!!