The series revolves around otaku teenager Tamotsu Denkigai and his sister Niwaka who are presently shopping in Akihabara, Tokyo, Japan. Suddenly, without warning, vampiric, cosplaying monsters known as "Bugged Ones" run rampant throughout the city. These creatures can possess anyone by biting them, and soon they cause total mayhem across the city. As Tamotsu is about to be attacked by one of these creatures, a mysterious girl wielding a baseball bat named Matome Mayonaka swings in and rescues him.
