Black Express leads the antagonistic Blatcher gang, a group central to the narrative's conflict. It wields an electric mace and is often shrouded in a cloak of black smoke, using the obscuring cloud for concealment and tactical advantage.

Under its command, the gang pursues a scheme known as Plan Operation Darkness, a primary driver of the series' conflict. Its subordinates carry out its orders, including the mild-hearted Dozilas, who enjoys playing with children, and the careless, daydreaming Wookary. The gang also commands Smoke Joe, a gigantic locomotive that emits a pervasive black smoke capable of obscuring everything in its path.

After a period of absence, Black Express and its gang return to Earth to resume their activities, prompting the reactivation of the counter-force JHR. Their methods involve a form of psychological manipulation, turning humans with positive, strong hearts into those with weak hearts, an action that aligns with their own ancestry and the objectives of Operation Darkness.