Akira Fudou attempts to rescue Ryou Asuka from the clutches of Oysnas, a demonic creature. However, their efforts result in an unexplainable time-travel phenomenon. Upon breaching a "Timeslip," Ryou identifies a recurrent invasion of past demons, who aim to interfere with crucial world events. With Akira and Ryou as the only hope, they must prevent the demons from manipulating historical figures, eventually amending human timespan's course.