In a small town in Japan, a series of seemingly random explosion cases occur. Ichiro Suzuki knowns as "Brain Man" is fingered as an accomplice. Midorikawa works on the explosion case.

The mysterious man known as "Brain Man" has outstanding memory, high intelligence and a perfect body, but doesn't seem to have human emotions. Neurosurgeon Mariko Washiya (Yasuko Matsuyuki), who has her own personal trauma, believes that human nature is fundamentally good and tries to save criminals. She then becomes interested in Brain Man and works to uncover the truth. Meanwhile, Detective Chaya (Yosuke Eguchi) tracks down Brain Man.