Himitsu: The Top Secret Episode 5

The stabbing death of a pharmacist that took place on a crowded train without an eyewitness, a series of murders of people from the same train car and an outbreak of a strange virus begin to resemble a bio-terrorism attack. Maki tells the others that it's possible that the murders happened at the same time by chance. Meanwhile, Yukiko, who was infected during an autopsy, declares that she will perform all autopsies on the infected who have died. Aoki urges Yukiko to infect him in order to hunt down the serial killer. In order to find the killer and the cure, Aoki volunteers to take the same train... (Source: Japanese = ktv.jp || Translation = mikilove13 at kisskh)