Episode 166

Izuku charges the memory of Kotaro beating a black void shaped like his son and slams into an invisible wall, the last armor around Tomura's origin. The scene plays on: Kotaro tells the boy that Nana, whose photo he uncovered that day, was a brute who walked out, and that heroes always wound their families to go help strangers. Nana finally understands that her son kept the picture because he could not make himself throw it away, and breaks down blaming herself for the hatred that consumed her grandson, and for a defeat that cost her any chance of returning home to mend things. Izuku calls for her; she dries her eyes, rams the barrier apart, and stops her son's hand. The act spends the final Factor the Quirk had left, so her vestige dissolves along with the memory, and she apologizes to her son for never returning and to her grandson for all of it, as the void peels back to reveal Tenko's frightened face. One For All ceases to exist, leaving only two boys.

Night falls, and Izuku finds Tenko crying against a wall as Decay manifests and reduces Mon to gore. Hana runs out screaming, Tenko chases her in a panic, and a child-sized Izuku locks hands with him and refuses to move. Asked why he is trying so hard, he says it is because he saw him cry. Tenko insists the destruction was deliberate and asks what else his hands could be for, then asks who is supposed to validate a birth like his. Izuku, who knows what it is to have someone take his hand, holds on until his arms crack and shred away at the biceps, telling him it will be okay, and the hatred melts. They kneel and touch heads. Tenko imagines playing All Might with Mikkun and Tomo, then sadly declines, accepting that a villain is what he is, and as visions of the League look down he becomes Tomura again and says the villains of the world need a hero too. Somewhere, a salaryman and a shut-in are still begging him to end everything. His mutated body starts to disintegrate, and unfamiliar memories surface: a construction associate recommending an excellent doctor to a younger Kotaro, then asking in a bar whether Tenko's Quirk has come in yet. The ground splits and a colossal scarred face rises out of it, swallowing Tomura and reclaiming the body, scolding the vessel for letting a nobody in. All For One lays it out: he found Kotaro years after All Might drove him into hiding, judged Hana too old to shape, and advised the couple to have a second child; he stole newborn Tenko's undiagnosed Factor, curdled Kotaro's resentment of Nana into abuse, arranged the play-dates and the truck rescue that made the boy love heroes, and walked him home to hand him Decay, a modified duplicate of Overhaul stripped of its healing. Tomura's vestige blows apart, the real body explodes into a wasteland, and "All For One" smooths into a grey shell, silencing the screams in his mind behind a black and red mask shaped like the hand.

Deku is left armless, both forearms destroyed in the vestige realm, and cannot stand. An Air Cannon aims at his head, Danger Sense fires, and Cellophane's Tape binds the villain before Tailman and Sugarman knock him down with Tornado Tail Dance and Sugar Knuckle. A Warp Gate opens, and Eraser Head steps out apologizing for the delay. Stranded on an ocean rock with Present Mic and "Kurogiri", he had watched Mic beat the Nomu bloody in frustration, then noticed tears and argued that a thing with nothing of Oboro left could have killed them both easily. The light they mixed into that darkness woke Oboro's face, weeping and saying Mic's real name. Mobile again, Eraser Head demanded a full battlefield status from Naomasa, gathered offensive heroes at Shiketsu including the retired Death Arms and Astro, took supplies from civilians including the young man who had opposed Deku's return, and accepted Eri's snapped-off horn, given because she wants to sing for everyone after the fighting and refuses to waste another chance to help. En route he cleared Takoba National Stadium of Gashly Eijiju. Now he taps the horn to Deku's shoulder, rewinding two or three minutes and returning his scarred arms, and tells him he cannot die before hearing Eri sing, while heroes pour out of the portals behind them.

Nana destroys the last barrier around Tomura's origin and vanishes along with the Quirk's last remaining Factor, ending One For All entirely, and Izuku reaches Tenko Shimura by holding his hands until his own arms are decayed away.

All For One seizes the body and reveals that he orchestrated Tenko's entire life, from arranging his birth and stealing his infant Quirk Factor to gifting him Decay, a modified duplicate of Overhaul.

Eraser Head returns through "Kurogiri" after reaching Oboro Shirakumo, brings reinforcements and Eri's broken horn, and Rewinds Deku's arms back onto his body as the surviving heroes arrive for the last fight.

The seventh episode of season eight adapts chapters 417 through 420, airing in Japan on November 15, 2025, with the dub on November 29.

The anime corrects a manga error, relocating the place where Deku says he first sensed the boy from Gunga to Jaku. It extends Nana's farewell with a wordless exchange of acceptance between her and Deku while cutting Kotaro's reaction to her apology, expands the scene of Izuku comforting Tenko, and lengthens the All For One and Kotaro flashbacks, the destruction of the vestige world, and the disguised walk home. Smoke-Eater and Lariat's flashbacks reuse footage from Episode 163, and Kai Chisaki's flashback precedes the Decay transfer.

Smaller adjustments: Hana stands farther from Tenko, more of Oboro's face appears inside Kurogiri, the U.A. flashback swaps Aizawa, Mic, and Oboro for three incidental students whose hairstyles resemble Sonic, Tails, and Knuckles, Kyoka's School Festival flashback is cut from Eri's dream, and the English dub uses young Tenko's screams when All For One hears the vestige.