There is a rumor going around about a CD called "Trigger" that can supposedly increase the intelligence of its listener. However, the CD has also been connected to several deaths and disappearances. Chitose's best friend Hayato listens to the CD, and not long after, Hayato and his whole family suddenly disappear. Refusing to believe that Hayato is gone forever, Chitose becomes determined to find his best friend and the truth behind the CDs.

(Source: The Zero Alliance)