Episode 4 (Vigilantes)

Three Sturm und Drang Brothers, a trio of sliding creeps, work the night streets until Knuckleduster drops all of them with a few swift punches. The Crawler checks them for Trigger and finds none, Pop☆Step asks the bystanders to call the police, and Knuckleduster, uncharacteristically grim, only says to keep moving. Koichi puts the mood down to his mentor's abrupt hunt for someone with a bee-related Quirk during the recent outbreak of Instant Villains. It carries into morning boxing practice, where Koichi's style refuses to mesh with his teacher's methods and he is told coldly that staying alive in a fight is his own problem to solve. Pop worries the training could kill him; Koichi insists the old man is holding back enormously, since a full-force punch would end someone.

Across the city, Kuin takes a call from her employer, who criticizes her wasteful use of Trigger during the swarm incident and tells her to concentrate on people with strong wills and powerful Quirks. That night she finds a furious street junkie, jams three vials into his neck, and tells him to funnel the rage into power and let society hear it. His muscles swell and his forearm bloats reddish-purple; he swings at her, misses, and she strolls off while he starts wrecking the district.

The Crawler barely dodges the new Instant Villain and stalls him while Pop leads civilians away, saving another bystander in the process. Knuckleduster swings in with a kick that puts the man through a wall, then insists on close-range brawling despite Koichi's advice to keep distance. He absorbs damage until the junkie greedily pauses to wind up a finisher, then slips it and knocks him cold with one clean shot to the face.

Knuckleduster reflects on the villain's speed, strength, and temper, seems to lament that this is the caliber they now face, then cheers at the prospect of it. By morning he is himself again, having simply been bored of street thugs who cannot fight back, though Pop still thinks he goes too far in training.

In a cafe, Kuin complains to her boss that the Naruhata Vigilantes intercepted her subject and that Knuckleduster is becoming a real obstacle. He argues the trio is useful, letting them gather data without heroes or police involved, and tells her to work around it. A nervous, blushing salaryman then arrives asking whether she is the "Honey" he is meeting, and she leaves with him, delighted.

Elsewhere, a sharp-toothed villain weaves through highway traffic at speed. Ingenium deploys from his team's truck, misses his grab, is told to run like his life depends on it, takes a kick to the head, and crashes into a wall as his costume's airbags fire. The next morning Koichi practices Slide and Glide and struggles with braking; a passing jogger startles him into a crash and then catches him. The man is Tensei Ida, who works as the Turbo Hero: Ingenium, and, hearing the problem, tells Koichi simply to push the repellent force in the opposite direction. Years of trouble evaporate instantly, and Tensei admires how flexible the Quirk is compared with the Engine he and his younger brother struggle to turn with.

Koichi doubts that raw speed matters much. Tensei disagrees sharply: people caught in an attack or a disaster are not asking to be saved, they are asking to be saved fast, and constant speed keeps hope alive as much as it moves anyone to safety. He offers a business card and a place on his support staff after graduation, explaining that Team Idaten makes room for anyone who wants their Quirk to do some good and that a license can come later. That night Ingenium strips the airbags for speed against his team's warnings, overtakes the villain into a padded roadblock, and loses him anyway when bat wings unfurl toward eastern Naruhata. Team Idaten cannot track him through the ward's dark, maze-like streets, but Koichi trips him mid-gloat and Knuckleduster finishes it. The vigilantes introduce themselves from above, Pop☆Step disowning both of them, and Ingenium recognizes The Crawler.

The next morning Tensei catches up to thank him. He accepts Koichi's denial of the secret identity without pressing, then politely asks for the card back, having decided the boy has already found where he belongs and not wanting to interfere. The disappointment is real, so Tensei cheers him up by daring him to sprint to the next corner and takes off.

Built from Chapters 6 and 7 of the Vigilantes manga. The Sturm und Drang sequence is heavily condensed, cutting their additional victims, their ideology, Koichi being attacked by women who mistook him for one of them, and his conversation with them about their similar Quirks; their crimes are also softened from panty theft to skirt-flipping. Voice casting identifies the Villain Factory boss as All For One far earlier than the manga does. Kuin injects the junkie herself rather than presenting a briefcase of samples for him to help himself to, and the anime adds her photographing a crepe during the call with her boss. Koichi cooking for his teammates and gushing over the business card at his penthouse is omitted, while Ingenium's introduction, Tenya's cameo, the flashback of him rescuing a girl from a fire, and Team Idaten's pursuit are all extended.