"Roots of the Problem", known as "Pitch-Black Numbers - Dark Yuma vs. Tetsuo" in the Japanese version, is the twentieth episode of the Yu-Gi-Oh! ZEXAL anime. It first aired in Japan on August 22, 2011 and in the United States on April 21, 2012.
At the top of a building, Yuma and Astral are Dueling a man, while Tori and Bronk are watching. Yuma controls "Number 39: Utopia", and his opponent 3 "Giant Germs". The man overlays his three monsters to Xyz Summon "Number 96: Dark Mist". However, it only has 100 ATK, surprising all of them. Yuma gets excited, thinking it is an easy win now, and declares battle between "Utopia" and "Dark Mist". Bronk and Astral both warn Yuma, but he still declares battle. "Utopia" succeeds in destroying "Dark Mist", and wipes out his opponent's last remaining 1000 LP, winning the Duel. Yuma is happy to win, and Tori smiles, but Bronk looks unhappy, most likely because of Yuma's reckless attack.
Astral absorbs "Number 96", and the memory regained is shown. In a view from space, cracks open on the Earth, and it explodes (in the dub, the planet is only covered in purple lines). Yuma and Tori celebrate the victory, with Bronk watching in the back. While going home, Yuma boasts about his victory and obtaining another "Number". Tori tells him to pipe down, and Bronk asks him about the recklessness of Utopia's attack. Yuma tells him it was fine, but Bronk heavily replies it wasn't. Yuma reacts saying he shouldn't worry, but Bronk grabs him. Yuma breaks loose and starts pinching Bronk, and Tori yells, telling them to stop.
The next day, Yuma and Bronk ignore each other on various instances. Inside the Emperor's Key, Astral presents Number 96 to a gear from his hand, inside the ship. He recalls the vision he saw when obtaining Number 96, and wonders what it means. Later, while lying on the school's roof, Yuma flashes back to the past, when a younger Yuma explains his ambition to his class. A young Bronk makes a comment about it, making the whole class laugh. Bronk also flashs back to those days, to the many Duels he and Yuma had, and Yuma's unbreakable spirit. However, despite them arguing during those Duels, they had a friendly rivalry, which Tori bore witness of.
Later, in the present, Tori questions the reason for his argument with Bronk, and Astral asks if he really means what he said. Yuma says he did, however, Bronk was in fact right in front of him. Yuma goes after him when he walks away, but when he grabs Bronk's shoulder, Bronk swings his arm, knocking the Emperor's Key of its rope. Almost immediately, black slime drools from Yuma's Deck case, streaming up, and enveloping Astral, who becomes visible to Tori and Bronk. However, the light parts of Astral's body became dark and black, and shocks start appearing on Astral. The black streams continue to pump the black sludge into Astral from multiple angles. Bronk sees where the Emperor's Key landed after the blow, and picks it up. Astral, while still getting shocked and the dark sludge is still being pumped into him, seems to talk to someone, saying they're Number 96. A voice from somewhere appears, and Astral's arms are being tilted up, with the sludge still being pumped into him. Astral screams out, and in a purple space, in Numbers-style, the number 96 appears. Number 96 is possessing Astral, while holding onto Yuma.
The darkened Astral gives them a malicious look, but the real Astral tells Yuma to entrust Bronk with "Number 39: Utopia". Yuma asks why, but Astral tells him to just do it. Yuma manages to pull Utopia's card out of his Deck, and throws it towards Bronk, who catches it, looks at it, and is surprised he threw him "Utopia".
Astral then is completely possessed by Number 96 , who declares himself the strongest "Number", and extends Astral's arm to grab "Utopia" back from Bronk (96 makes no claim of being the strongest in the dub. This, however, is prevented by the Emperor's Key, which creates a shield around Bronk. Tori asks if he is okay, which he confirms, but is worried about Yuma. Number 96 looks at Bronk angrily. The latter thinks about a way to save Yuma and Astral from Number 96. Bronk tells him that if he wants Utopia, he should Duel him. Number 96 agrees, and lets Yuma free, deciding he'll use him as a puppet. Controlling Yuma's actions, the Duel starts, and Number 96 uses Yuma's Deck.
During the Duel, Number 96 quickly Summons his own card, "Dark Mist". However, it looks different than in Yuma's Duel against its original holder. 96 explains that this is Number 96's, his own, true form. Number 96 actually uses its effects during the Duel, revealing it willingly manipulated its holder into losing in order to get to more "Number" cards. Bronk is able to Summon "Utopia" in a reaction to "Dark Mist". The will-enforcing effect of the "Numbers" appears to take over Bronk, but he seems to be able to shake it off.
Using the effects of Yuma's Deck after he enhanced it with cards from the Duel Sanctuary's secret Deck and some extra anti-Xyz cards, Number 96 obtains an edge over some of Bronk's moves. During the Duel, Astral manages to get in contact with Yuma. In a mysterious space, Astral is hanging, with his body slowly fading away. After Bronk finishes his turn, Yuma suddenly collapses, getting back up. He stands in a zombie-like stance, and Number 96 laughs, saying he now controls Yuma too. Number 96 ends up destroying "Utopia" relatively easy, and "Dark Mist" now has 3100 ATK.
Yuma explains to 96 that he should be careful of Bronk's face-down card, as its most likely the card "Gearspring Exploder", which, if used, could win Bronk the Duel at the moment. Not happy to hear it, Numbers 96 responds to this by activating the Quick-Play Spell Card "Xyz Cyclone", to destroy "Gearspring Exploder". Number 96 thanks Yuma for giving him warning about the facedown card. Bronk seems devastated by Yuma being under 96's control and also the fact that he had sold him out, but flashes back to Yuma yelling he will never give up. He then continues the Duel with a combo between "Automatic Gearspring Machine", "Gearspring Spirit", "Gearspring Catapult" and a "Monster Reborn"-revived "Utopia". Before Bronk defeats Number 96 Yuma starts snickering, and tells Bronk he did great. Number 96 is shocked to see that Yuma wasn't under his control at all, and Yuma explains it was a trick to make sure Bronk would still have his "Catapult" and "Automatic Machine".
Bronk, while declaring that he is "feeling the flow," destroys "Dark Mist" with "Utopia". He then tosses the Emperor's Key to Yuma, which releases Astral from the prison created by Number 96. Astral appears in the sky, and re-absorbs Number 96. Yuma and Bronk happily run to each other. Bronk gives Yuma "Utopia" back, while asking how he came up with the idea of tricking Number 96. Judging from his reaction, Bronk figures it was Astral's plan, and the two get into an argument over it. Above them, Astral says Yuma and Bronk saved him. Looking at Number 96's card, he figures there is something up with it. He asks if there were other memories like it.
Yuma Tsukumo vs. Number 96's holder
"Utopia" attacks and destroys "Dark Mist" (Number 96's holder: 1000 → 0 LP).
Bronk Stone vs. Number 96
Turn 1: Bronk
Bronk draws "Aye-Iron" and subsequently Normal Summons it (1600/1800). He then equips it with "Spring Punch". Whenever "Aye-Iron" gains ATK, half of its ATK will be inflicted to the opponent as damage and that turn's Battle Phase will be skipped. Bronk activates the effect of "Aye-Iron", increasing its ATK by 400 ("Aye Iron": 1600 → 2000 ATK) and preventing it from attacking this turn. "Spring Punch" inflicts 1000 damage as the ATK of "Aye-Iron" was increased (Number 96: 4000 → 3000 LP). Bronk activates the "Gearspring Catapult" Continuous Spell Card. During each of his Standby Phases, it will gain a Gearspring Counter. Bronk can then remove a Gearspring Counter to increase the ATK of a monster by 500.
Turn 2: Number 96
Number 96 draws "Acorno" and subsequently Special Summons it (200/400) in Attack Position by discarding "Pinecono". As "Pinecono" was sent from the hand to the Graveyard, its effect activates, Special Summoning itself (400/200) from the Graveyard in Attack Position. He then Normal Summons "Darklon" (100/100). Its effect activates, increasing the Level of all of his monsters by 1 ("Acorno", "Darklon" and "Pinecono": 1 → 2) and changing their Attributes to DARK. Number 96 overlays his Level 2 DARK "Acorno", "Pinecono" and "Darklon" to Xyz Summon "Number 96: Dark Mist" (100/1000, ORU: 3) in Attack Position. "Dark Mist" attacks "Aye-Iron". As "Dark Mist" is battling a monster, Number 96 activates its effect, detaching an Overlay Unit ("Dark Mist": 3 → 2 ORU) to halve the ATK of "Aye-Iron" and add it to that of "Dark Mist" ("Aye-Iron": 2000 → 1000 ATK, "Dark Mist": 100 → 1100 ATK). "Aye-Iron" is destroyed (Bronk: 4000 → 3900 LP). Number 96 Sets two cards.
Turn 3: Bronk
Bronk draws. During the Standby Phase, "Gearspring Catapult" gains a Gearspring Counter. Bronk Normal Summons "Tin Goldfish" (800/2000) and activates "Iron Call", letting him Special Summon a Level 4 or lower Machine-Type monster from his Graveyard. He Special Summons "Aye-Iron" (1600/1800) in Defense Position. Bronk activates "Iron Draw", drawing two cards as he controls two face-up Machine-Type monsters. He then overlays his Level 4 "Tin Goldfish" and "Aye-Iron" to Xyz Summon "Number 39: Utopia" (2500/2000, ORU: 2) in Attack Position. Bronk activates the effect of "Gearspring Catapult", removing a Gearspring Counter to increase the ATK of a monster by 500 ("Utopia": 2500 → 3000 ATK) until the End Phase. "Utopia" attacks "Dark Mist", but Number 96 activates the effect of "Dark Mist", detaching an Overlay Unit ("Dark Mist": 2 → 1 ORU) to halve the ATK of "Utopia" and add it to its own ("Utopia": 3000 → 1500 ATK, "Dark Mist": 1100 → 2600 ATK). Bronk activates the effect of "Utopia", detaching an Overlay Unit ("Utopia": 2 → 1 ORU) to negate his own attack. As an attack between two Attack Position monsters was negated, Number 96 activates his face-down "Counterforce", inflicting damage to Bronk equal to the difference between their monsters' ATK (Bronk: 3900 → 2800 LP). Bronk activates "Automatic Gearspring Machine", which gains two Gearspring Counters and will gain another one during each of Bronk's Standby Phases. He may then send it to the Graveyard to move its Gearspring Counters to another card that can use them. Bronk Sets a card.
Turn 4: Number 96
Number 96 draws. "Dark Mist" attacks "Utopia", with Number 96 activating the effect of "Dark Mist", detaching an Overlay Unit ("Dark Mist": 1 → 0 ORU) to halve the ATK of "Utopia" and add it to that of "Dark Mist" ("Utopia": 1000 → 500 ATK, "Dark Mist": 2600 → 3100 ATK). Bronk activates the effect of "Utopia", detaching an Overlay Unit ("Utopia": 1 → 0 ORU) to negate the attack, but Number 96 activates his face-down "Overlay Banish", negating the effect of "Utopia" as it was activated during the Battle Phase by detaching an Overlay Unit. The attack continues and "Utopia" is destroyed (Bronk: 2800 → 200 LP). At this moment, Number 96 plans on destroying "Gearspring Catapult" to prevent Bronk from increasing his monster's ATK, but Yuma says that's not his plan and reveals that Bronk's face-down is "Gearspring Exploder" and explains its effect. Number 96 activates "Xyz Cyclone", destroying Bronk's face-down "Gearspring Exploder" as a monster he controls destroyed an Xyz Monster.
Turn 5: Bronk
Bronk draws. During the Standby Phase, "Gearspring Catapult" and "Automatic Gearspring Machine" each gain a Gearspring Counter. Bronk removes three Gearspring Counters from the latter card to Special Summon "Gearspring Spirit" (100/100) from his hand in Attack Position via its own effect. He then activates the effect of "Gearspring Spirit", decreasing the ATK of a monster his opponent controls to 0 ("Dark Mist": 3600 → 0 ATK) until the End Phase. Bronk activates "Monster Reborn", Special Summoning "Utopia" (2500/2000) from his Graveyard in Attack Position. He then activates the effect of "Gearspring Catapult", removing a Gearspring Counter to increase the ATK of a monster by 500 ("Utopia": 2500 → 3000 ATK). "Utopia" attacks and destroys "Dark Mist" (Number 96: 3000 → 0 ATK).
The following cards appeared in this episode. Cards in italics debuted here.