Shotaro: "Danger is always by my side. That's a detective's fate."
Kirihiko: "Strong feeling like anger or hatred can change a human's body or mind into a Dopant!!"
- The V stands for "Virus" and "Vehicle."
- The first part is "Infected Car."
- Part two is titled "Grudge Beast."
At the Narumi Detective Agency, Akiko has fallen ill with a cold and calls Shotaro an "idiot who never catches a cold", spurning Philip's interest in this phrase despite not knowing that it is an idiom. The agency then gets a phone call from a man named Mikio Aoki who claims that he is being chased and needs help. When Shotaro arrives on the scene, he comes across the man before seeing a black SUV run through him, causing the man to writhe in pain before falling down dead. When Shotaro is taken in for questioning at the police station the next day, Makura thinking that he murdered Aoki, Jinno arrives to reveal that Aoki died from a mysterious disease. Deciding to get to the bottom of it, Shotaro learns from Watcherman that Aoki was a member in a chop shop street gang. They head to the gang's usual hangout to talk to its leader Kurosu. Shotaro questions him, until Kurosu pulls a gun on Shotaro after one member of his posse hints that the SUV was stolen. Akiko, scared for their lives, drags Shotaro out before the other two gang members leave and talk about checking out the SUV. Shotaro trails them as the SUV appears once more to run down the other two members, killing one of them before chasing after the other. Shotaro contacts Philip to transform as Philip is still investigating the idiom. Shotaro instead activates the Bat Shot to take photos of the driver, eventually transforming into Kamen Rider Double to save the younger gang member before the Nasca Dopant intervenes. This allows the SUV to run down the gang member. Later, Philip identifies the driver as Kōhei Yamamura, whose older sister Sachi Yamamura was hit by a car driven by Kurosu's gang and is currently in the hospital in a coma. Believing that Kōhei is the Dopant, Shotaro confronts him and accuses him of it. Kōhei runs off into a bus to escape to continue his revenge, succeeding because Sachi's fiance Noriyuki Yushima just got off the bus and holds Shotaro at bay. After talking to Yushima and learning about Kōhei, Shotaro gets a call from Akiko that she has followed Kurosu to a warehouse so he can gun down Kōhei in the SUV. Kamen Rider Double arrives at the warehouse on the HardBoilder, provoking Kōhei to chase after him. Assuming HeatMetal and using the RevolGarry, Double manages to wreck the SUV without being infected. While inspecting the wreckage with Akiko, they cannot find a Gaia Memory just as the real Virus Dopant makes itself known.
Revealing itself, the Virus Dopant kills Kurosu as Kamen Rider Double is powerless to keep the monster from running away as Shotaro senses sadness from it. The next day, after reviewing the how the hit and run on Sachi began the Virus Dopant's attack, Shotaro believes that Yushima is actually the Dopant. Heading to a girl school where Yushima teaches art, Shotaro finds the Virus Dopant attacking Yushima. Double saves Yushima and fights the Dopant before it runs away. Back to square one, Akiko believes that Sachi may be the guilty party. Though Shotaro could not believe it, Akiko and Philip visit the hospital where Sachi is being kept and he finds her Living Connector. Philip concludes that the Virus Dopant is formed from Sachi's consciousness, and seeks to contact her through the Gaia Library. Upon meeting her, she tells Philip that just before she received the Virus Memory, she caught Yushima proposing to another woman. Elsewhere, Shotaro learns from Queen and Elizabeth that Yushima is a casanova who uses women for his art. When Shotaro goes to confront him, he arrives just as the Virus Dopant is about to kill Yushima. Shotaro begs the monster to stop while he forces Yushima to apologize to Sachi. Neither Shotaro nor Philip can reason with Sachi, leading the powers of the Virus Dopant to take over, forcing them to transform into Kamen Rider Double to fight the Virus Dopant. After Philip realizes that the only way to defeat the Dopant is to completely destroy it, Shotaro decides that they transform into HeatTrigger and use the Trigger Explosion Maximum Drive to deal the deathblow. The Virus Dopant is vaporized and the Virus Memory is ejected from Sachi's body and breaks. Soon after, Shotaro punches Yushima for causing the deaths of the four gang members by breaking Sachi's heart. A few days later while closing the case, Shotaro begins showing symptoms of a cold.
- Asshole Victim: The gang members. Philip and Akiko even question if they really deserve Shotaro's efforts to save them.
- Clear My Name: Shotaro is initially implicated as the autopsy of the first death reveals no injury from the car crash.
- Hey, It's That Guy!: one of Yushima's arts students was Amane from Kamen Rider Blade.
- And GingaGreen is one of the shady men whom the Virus Dopant targets.
- Karma Houdini: No arrests are made, and Yushima even gets away with his life. Although Shotaro does manage to punch his lights out.
- Karmic Death: the black SUV was created from the Virus Dopant's use of car parts from the chop shop.
- Stringy-Haired Ghost Girl: Shachi
- Superpower Lottery: The fluke of using the Virus Memory when near death actually altered its properties.
- Van in Black: variation, the SUV is the antagonist for a while.
- Woobie, Destroyer of Worlds: Sachi reeeeally had it rough. In the end, Shotaro wasn't trying to save her victims as much as he was trying to save her.