Plot
A doomsday cult known as Humarise believes that Quirks will eventually become so powerful that they will bring about the extinction of humanity. Because of this, they have planted bombs all over the world filled with "Trigger" gas which kills Quirk users by driving their Quirks out of control and dying in the process. Their leader, Flect Turn, plans to use these bombs to save humanity by killing the Quirk population.
After Humarise detonates its first Trigger Bomb, the World Heroes Association dispatches Pro Heroes and U.A. High Hero Course students to Humarise's targets in hopes of disarming the remaining bombs. Izuku Midoriya, Katsuki Bakugo, and Shoto Todoroki are among those sent to Humarise's supposed main headquarters in the country of Otheon. None of the Heroes find any trace of Humarise and they are put on standby. During an outing, Izuku, Katsuki, and Shoto encounter a jewel robbery in progress. Shoto and Katsuki pursue the thieves while Izuku gives chase to their courier Rody Soul, a street urchin who took the job to provide for his younger siblings.
Meanwhile, Alan Kay, a Humarise scientist, flees with an important briefcase but is attacked by a Humarise agent, Beros, and he crashes his car in the midst of Izuku and Rody's chase. Rody accidentally grabs Kay's briefcase shortly before Izuku catches him. They are soon attacked by the police, but Izuku escapes with Rody using Blackwhip. Izuku is publicly accused of mass murder by Otheon's chief of police, who is a member of Humarise, and goes off the grid per Shoto's advice. Izuku and Rody make their way to the neighboring country of Klayd, where the Otheon police will not have jurisdiction. Izuku sends a coded message about his new destination to Shoto, who heads off with Katsuki to join him there.
That night, Rody becomes homesick and secretly reports the briefcase to the police. The officers that arrive turn out to be Humarise agents, who attack him. Having been woken up by Rody's bird companion Pino, Izuku saves him, but is wounded by Beros during the fight. Rody apologizes to Izuku while patching him up, explaining how his father abandoned the family to join Humarise, and that he and his siblings were ostracized as a result. The two are attacked at the Klayd border by Beros, but are saved by Katsuki and Shoto, while Beros commits suicide in order to evade capture.
Later, Izuku discovers a hidden compartment in the briefcase containing a puzzle which Rody played with as a kid. Rody solves it and finds a USB device and a data disk inside. The disk contains a message from Kay, who reveals that he and Eddie Soul, Rody's father, were forced by Humarise to create the Trigger bombs; the device contains a kill code for the bombs created by Kay and Eddie. Humarise announces that they will detonate their remaining bombs in two hours, forcing the deployed Heroes to scramble in defense to find them and fight the Humarise soldiers. Izuku and the others head to Humarise's headquarters with the device on a plane piloted by Rody.
Katsuki and Shoto deal with high-ranking Humarise villains, while Izuku faces Flect Turn, whose Quirk reflects whatever comes into contact with him. Izuku is overwhelmed by Flect Turn's natural defenses, as well as his laser barrage. Rody arrives and seemingly betrays Izuku by handing over the device in exchange for his siblings' safety. Thanks to Pino, who is actually Rody's sentient Quirk which expresses his true feelings and intentions, Izuku realizes it is a feint and catches Flect Turn off guard. Realizing that Flect Turn's Quirk has a limit to how much damage it can take, Izuku uses One For All at 100%, to defeat Flect Turn with a barrage of attacks.
Meanwhile, Rody heads for the Trigger Bombs' control system, and despite being wounded by the laser defense system, he and Pino barely manage to insert the device in time, preventing the Bombs from activating. In the aftermath, Humarise's surviving members are arrested, while the Heroes are healed at the hospital. As Izuku heads back to Japan, he and Rody bid a tearful goodbye to each other. Class 1-A reunites back at U.A., while Rody gets a job at the local bar, and also pursues his dream of becoming a pilot.
