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Cronos de Medici (クロノス・デ・メディチ) (Vellian Crowler)
The head Obelisk Blue professor at Duel Academy, and initial (albeit non-lethal) antagonist. Looks down upon Osiris/Slifer Red students, particularly Jaden, whom he calls "drop-out boy".
He uses an Ancient Gear deck.
Voice actor: Hiroshi Shimizu (Japanese) and Sean Schemmel (English)
- Accent Adaptation: Despite being Italian hes given a pronounced Mid-Atlantic accent in the dub.
- Advanced Ancient Acropolis: Crowler's deck is based on this theme. His Ancient Gear monsters are implied to be Lost Technology, and some of his other monsters stem from Classical Mythology, such as the Trojan Horse.
- Agent Peacock: You probably wouldn't be able to tell just by looking at him that a man as foppish as he wields a deck exclusively loaded with burly, rusted, monstrous machines.
- Ain't Too Proud to Beg: Begs desperately to Aster to get him to show Chazz how to be a pro duelist in Season 4.
- And Then John Was a Zombie: Temporarily turned into a Duel Ghoul (or Zombie) in Season 3 when duel academy was sent to the different dimension by Yubel.
- Anti-Hero: The classic kind. He's cowardly and snobbish, but still on the side of good.
- Armor-Piercing Attack: The main gimmick of the Antique Gear deck is that whenever an Antique Gear monster attacks, the opponent is forbidden from activating any Magic or Trap cards in response, which often ends in a destroyed monster. Antique Gear Golem and Ultimate Antique Gear Golem also have a piercing effect, so the opponent still loses Life Points even if the monster is in Defense mode.
- As Long as It Sounds Foreign: He says some Italian phrases (and foods) every so often in the original version.
- Badass Teacher: He has his moments.
- Beauty = Goodness: Averted when he was a villain but played straight when he becomes good.
- Butt-Monkey: He's often the butt of many jokes, especially during the first season as a Sadist Teacher. He is however, a lot more respected in the Japanese version.
- Clockwork Creatures: His Ancient Gear Deck.
- Cool Teacher: By season 4. He helps Alexis and Chazz find their paths for after they graduate, he even begged Aster to show Chazz how to be a pro duelist.
- Crippling Overspecialization: His Ancient Gear deck prevents activation of Magic and Traps when his Ancient Gear monsters attack. Unfortunately for Crowler, this doesn't include Monster Effects, which run rampant in GX and are usually his downfall. His deck is also strongly centered around Ancient Gear Golem. If Golem is destroyed or incapacitated, or if is strategy for summoning it is interrupted, he's usually in big trouble.
- Crouching Moron, Hidden Badass: Despite being used mostly as Plucky Comic Relief after Jaden defeats him in the pilot, he has his moments. He tends to vigorously defend his students when they're in peril, even at great danger to his own life. And when it's time for him to duel, he always has a way to get his beloved Ancient Gear Golem on the field no matter what his opponents throw at him, at which point it's time to clean house.
- Deus Exit Machina: He is without his deck during the Dimension Arc, and thus can't duel. This does however, allow him to survive it unscathed.
- Dishing Out Dirt: His Ancient Gear monsters are all EARTH.
- Dude Looks Like a Lady: Though definitely not in a Bishonen way...
Museum guard #1: I didn't know he was a doctor.Museum guard #2: I didn't know he was a dude.
- The dub, in particular, had a field day with this. For example:
- Evil Is Petty/Sore Loser: His initial antagonism towards Jaden, which varied from attempts at getting him expelled to him going missing or being outright killed, was fueled from his anger at not being able to stand the idea that he could lose to a "slacker" like him.
- Explosive Overclocking: The "Limiter Removal" spell card doubles all machine monsters' attack power but destroys them at the end of the turn. Crowler uses Limiter Removal to win his duel with Chumley by powering up his Ancient Gear Golem so it's stronger than Chumley's Master of Oz. The Golem's being destroyed doesn't matter because it defeating Chumley's monster wipes out his Life Points.
- Expy: Of just about every teacher unfortunate enough to antagonize Yugi and his friends. However, he does become a lot nicer later on.
- Flanderization: Similar to Kaiba in the previous series, his Jerkass character traits are turned Up to Eleven in the dub, to the point where he makes condescending and rude comments during scenes where he is actually very nice and respectful in the original. Most notably during Chumley's graduation duel, where his lines don't even really fit the animation.
- Gonk: Just because he looks like a lady does not mean he's pretty. After defeating him and turning him into a doll, Camula immediately discarded him over his looks.
- Hate Sink: Initially, Crowler is portrayed as extremely smug, petty, and unreasonable with an irrational hatred toward Jaden, making him very easy to dislike. He eventually mellows out, though.
- HeelFace Turn: He starts off antagonistic to Jaden, but eventually comes to like and respect him. The point of the turn started during the Shadow Stars arc and continued after then.
- Hidden Depths: He's a very capable duelist who usually only loses because of the plot and a good enough teacher that even Jaden, who by his own admission sleeps through most classes, has been known to quote his lessons. When he dueled Chumley, even though Chumley lost, he was impressed enough by Chumley's performance to still recommend him for a job at Industrial Illusions, despite his claim that he would expel him on the spot if he lost.
- Hypocritical Heartwarming: He's the only teacher allowed to call the Osiris Red students "worthless" if he has anything to say about it. Bonaparte learned this the hard way.
- It's Personal: He's not very fond of the Reds as a whole, but he has it out for Jaden in particular for having the gall to show up late and then humiliate him in a Duel. A big part of his Character Development involves him getting over it.
- Jerkass Has a Point: His personal grudge for Jaden aside, his overall dislike for the Osiris Red students does have valid reasons since duel monsters are Serious Business by their current time and any underperforming student treating it as some run-of-the-mill children's card game where it can be a potential career occupation would be something that Crowler would be intolerant of. His initial dislike of Judai is also based on the latter's cavalier attitude, which actually does cause some serious problems down the road and is called out by others.
- Jerkass to One: Overall, he doesn't have a good opinion of the Osiris Red students mostly from the result of the elitist dorm system in the Academia and duel monsters being Serious Business, but when it comes to Jaden specifically, then Crowler would stop being reasonable altogether and find any excuse to expel the latter. It's only until Character Development to where Crowler starts to let bygones be bygones.
- Jerk with a Heart of Gold: He's very disparaging of Jaden and his friends, calling Jaden "dropout boy" in the original and referring to them collectively as "Slifer slackers" in the dub, but is more than willing to lay his life on the line for his students, even Jaden. As time goes on, he becomes a lot closer to Nice Guy than Jerkass.
- Large Ham: Extremely overdramatic. Just watch the episode where he tries to keep the students from graduating.
- Magic Poker Equation: A bizarre example as this trope completely works against him more often than not. He's obscenely lucky in his starting draws to the point that he'll have the means (of which he has a lot of in his deck) to summon an Ancient Gear Golem in his first few turns if not the very first. But because this would necessitate a Drama-Preserving Handicap to stop him from winning right away, his opponents will have just the right counters to survive or even neutralize his Golem's attacks.
- Meaningful Name: His given name is one to the Greek titan, Cronos, which fits well with the overall theme of his Ancient Gear monsters. Also, his surname is one to the Medici family, an Italian noble family who ruled Florence and Tuscany during the Renaissance period.
- Non-Action Big Bad: For the first half of the opening season, he tries various ways and commissions a number of proxies to try to expel Jaden or at the very least make his life at school miserable as he can't do so with a straightforward rematch.
- One-Winged Angel: His Ancient Gear Golem can be fused with two other Ancient Gear monsters (Crowler uses all of his Golems specifically) to create Ultimate Ancient Gear Golem, an even bigger 4400 ATK/3400 DEF behemoth that has all of the Golem's effects, plus one: it revives a Golem to the field if it is destroyed.
- Sadist Teacher: In the first half of season 1, where his story arc consists of him finding various inane excuses to try and get Jaden expelled.
- Signature Move: Ancient Gear Golem, a 3000 ATK/3000 DEF behemoth that deals damage to Life Points regardless of if the target monster is in Defense mode or not, in addition to the standard "Ancient Gear" ability to prevent Magic and Trap cards from activating during its attacks. He has three of them and a plethora of ways to summon them.
- So Proud of You: In season 4 after his rematch with Jaden, he admits that he enjoyed being the teacher of Jaden and the others, and actually sheds Tears of Joy at losing.
- Stern Teacher: Taking a level in kindness does not mean that Jaden gets let off for missing so many classes.
- Token Adult: In Season 3 during the Dimension World arc.
- Took a Level in Kindness: Starts creeping in more and more as the series goes on. At the end of Season 1, despite beating Chumley in their duel, Crowler expresses genuine admiration for his dueling skills and allows him to graduate. He also is shown clapping with everyone else after Jaden and Zane tie in their duel in the season finale. In Season 2, he goes on to defend the red dorm (something that would have seemed wildly out of character at the start of the character). By Seasons 3 and 4, he is practically a Nice Guy. Depending on interpretation, he could be seen as always having been a nice guy with some wounded pride over losing to Jaden.
- Tooth Strip: A notable aversion; his teeth are usually drawn distinct from each other. Doesn't exactly help his already odd appearance, especially when he was turned into a doll.
- Verbal Tic: "Na no ne" in the original Japanese.
- Worf Had the Flu:
- He loses to Camula due to her using vampire bats to spy on his deck in order to learn how it works ahead of time. Fortunately her bragging about this allowed Zane and Jaden to work around that.
- Due to being pulled into the portal only by accidental proximity, he's without his deck and can't duel for the latter half of season 3.
- Younger Than They Look: He looks far older than the 35 he actually is.
Kabayama (樺山) (Sartyr)
The head of the Ra Yellow dorm and unfortunately the least featured of the 3 main professors.
He uses an anime exclusive spice deck.
Voiced by: Yuichi Nagashima (Japanese) and Marc Thompson (English)
- A Day in the Limelight: After barely making any significant appearances throughout season 1, he finally gets an episode focusing on him as well as getting lines and his own duel.
- The Cameo: Has several throughout the series which is the majority of his screen time.
- Cooking Duel: A literal example where he used his monsters to cook in a card effect.
- Forgettable Character: He puts Bastion to shame on how many people forgot he existed and was a teacher who worked at the Academy.
- Hates Being Alone: His main reason for trying to get the Ra students back to their dorm is because most of his students have graduated to Obelisk Blue dorm.
- Hidden Depths: Despite being a teacher at the academy he is an accomplished chef and is skilled card designer.
- Large Ham: Has shades of this especially when he is Curry Mask.
- Out of Focus: Despite being the head of one of the three main dorms, he hardly gets any significant screen time aside from a few cameos.
- Paper-Thin Disguise: Literally. He wears a paper bag over his head to disguise himself.
- Supreme Chef: He is very good at cooking and used his skills to lure the students out of the red dorm.
- Through His Stomach: He uses this tactic in order to try to convince the Ra Yellow students in the Slifer Dorm to come back to Ra Yellow.
Daitokuji (大徳寺) (Lyman Banner)
He uses an alchemy-themed deck based on removing monsters from play.
- Absent-Minded Professor: Naturally, although he's clearly faking it most of the season.
- Affably Evil: Even when he reveals his true colors as Amnael, he remains polite and personable.
- Alchemy Is Magic: Well, he never says so, but the way he uses it, it sure seems like it.
- As Long as It Sounds Foreign: His accent in the dub is Germanic and even stronger as Amnael. Justified, seeing as many famous alchemists were German.
- The Atoner: After his defeat as Amnael, he provides an instrumental piece to defeat Kagemaru.
- Badass Bookworm: He can put up quite the fight with his alchemy-themed deck while punctuating it with a lecture about alchemy.
- Badass Teacher: Far more than he appears to be at first.
- Badass Cape: Sports a billowing, hooded grey cape upon assuming the identity of Amnael. He then proceeds to thoroughly school several of the protagonists.
- Beware the Nice Ones: Certainly the nicest of all of the teachers at Duel Academy. And also one of the Seven Stars/Shadow Riders.
- Blood from the Mouth: Happens in a flashback explaining how he contracted a fatal illness.
- The Bus Came Back: He returns as Amnael, defeats Chazz and Alexis, takes their keys and nearly defeats Jaden.
- The Chew Toy: Literally! After becoming a Spirit Advisor, he's often swallowed by his cat Pharaoh.
- Cool Teacher: In the first opening, "Kaisei Josho Hallelujah", you can see him on a motorcycle. And in episode 13, he sicces his cat Pharaoh on some evil scientists.
- Crippling Overspecialization: Aside from the fact that his Alchemy Beasts are capable of attacking his opponent directly, at its core, Amnael's deck revolves around banishing his own monsters to beef up the ATK of his Golden Homunculus and Helios cards. Once Jaden manages to summon Elemental HERO Electrum, his entire playing style is rendered useless as his cards that were banished are returned to his deck.
- Crouching Moron, Hidden Badass: His airheadedness is probably genuine. Regardless, he's the strongest of the 7 Shadow Riders and is able to defeat half of the main cast.
- Double Agent: He took the job at Duel Academy in order to gain access to Spirit Keys.
- The Dragon: As Amnael. He is the strongest Seven Stars Assassin/Shadow Rider.
- Easily Forgiven: No one seems to hold the fact that he is Amnael against him after he is defeated. Then again, he is just a disembodied spirit afterward.
- Evil Mentor: To Jaden, whether or not Jaden recognizes him as such or appreciates it.
- Evil Sounds Deep: While masked, Amnael's voice in the dub is much deeper than Banner's usual voice.
- Eyes Always Shut: He only opens them when he duels Jaden as Amnael.
- Gentleman Snarker: Everyone in the dub is pretty snarky, but only Banner can remain ever so polite while bringing the sass.Crowler: (After Jaden and Syrus beat the Paradox Brothers) This can't be! How'd they win? It's not fair...
Banner: How? Because of your superb teaching, of course. Oh wait, they're in my dorm.
- I Am Not Left-Handed: His Alchemy Deck is pretty strong. He defeats Chazz, Alexis, and nearly Jaden.
- Killed Off for Real: Both his original and clone bodies turn into dust, however, his spirit sticks around, mostly because Pharaoh refuses to let him move on to the afterlife and keeps him in his stomach.
- Kindhearted Cat Lover: Think about it. He has a cat, he says "nya" at the end of his sentences? That's proof enough.
- Mask Power: As Amnael, although he ditches it after The Reveal.
- Mentor Occupational Hazard: Interestingly, he becomes more of a mentor after his death.
- Nice Guy: Quite possibly the nicest teacher in the Academy, which almost makes up for the Slifers getting treated like crap by everyone else. It goes away somewhat when he turns up as Amnael, but comes right back when the mask comes off, indicating that he was never pretending to be nice and really is just that friendly.
- No-Sell: His Elemental Absorber trap card renders him immune to any of his opponents' monster attack by banishing a monster card from his hand with the corresponding attribute.
- Obfuscating Stupidity: He plays the part of the scatterbrained professor as a part of his cover. Though it might not all be an act.
- Our Homunculi Are Different: He caught a fatal illness and created a new body to put his soul into, leaving the original to mummify. His current body is slowly falling apart, which he's hoping to remedy with the power of the Sacred Beasts. After losing to Jaden and entrusting him with the means to fight Kagemaru, both the homunculus and his original body turn to dust.
- Put on a Bus: He suddenly disappears during the SSA arc. For good reason.
- Red Eyes, Take Warning: As Amnael, when he finally opens them, they're blood red, and not at all pleasant to look at.
- Right-Hand Cat: His cat Pharaoh.
- Spared by the Adaptation: Played with. While 4Kids did not edit out his "death", in the original version, Kabayama/Sartyr is aware that Daitokuji/Banner passed away. In the dub, Kabayama/Sartyr is still under the impression that he's missing.
- Spirit Advisor: To Jaden, against Kagemaru and a few times afterward.
- Treacherous Advisor: Seems that way at first, but later proves to have Jaden's best interests in mind.
- Verbal Tic: Japanese version only - while Daitokuji-sensei often says "nya" (Japanese for a cat's meow) at the end of his sentences, other languages eliminate it altogether, and give him a German accent because he teaches alchemy.
- White Hair, Black Heart: As Amnael.
- Why Did It Have to Be Snakes?: Has a fear of vampires above all else; when it's revealed that one of the Shadow Riders is one, he freaks out and pulls every vampire-repelling trick in the book.
Samejima (鮫島) (Sheppard)
Duel Academy's principal and former master of the "Cyber Style", which Zane inherited.
He uses a Cyber deck, with Cyber Ogre 2 as his trump card.
Voiced by: Masami Iwasaki (Japanese) and David Wills (Engish)
- Adults Are Useless... and depressed by his awareness of that.
- Bald of Awesome: He hasn't got a hair on his head, and he deserves credit where it's due - despite not doing much as an authority figure, he's not half bad as a duelist. It's just that Zane is better.
- Nice Job Breaking It, Hero!:
- He has a pretty serial case of this, to the point where most of the problems in the series can be traced to him. In the first season, he failed to tell anyone about Kagemaru despite knowing who he was, and handed the Keys to prominent students instead of just tossing them off a bridge.
- He left for most of the second season to let Crowler and Bonaparte run the school and allowed the Society of Light to take root, and when he came back, he started the GeneX Tournament, which failed to attract the person it was meant to attract or redeem the person it was meant to redeem, and decided to comply with Sartorious' request to invite Ojin, indirectly handing the laser satellite to him.
- Season 3 would have gone a lot differently if he hadn't brought Professor Cobra to Duel Academy, making his scheme possible. To make matters worse he leaves again just as all of the students are passing out due to the Dis Bands.
- Old Master: Of the Cyber Style of dueling, of which Kaiser/Zane is also a practitioner. Kaiser has long since surpassed him in this regard, of which he is painfully aware.
- Reasonable Authority Figure: When he knows what he's doing. The students are overjoyed in Season 2 when he returns from his sabbatical to replace the head-butting Crowler and Bonaparte, but his ridiculously bad judgment continuously allows the villains' plans to take flight. This gets worse and worse, to the point where in Season 3 it's Crowler and Bonaparte who are the reasonable ones who want to shut down Professor Cobra's dis-duels.
Emi Ayukawa (鮎川恵美) (Fonda Fontaine)
Duel Academy's nurse, gym teacher, and the head of the Obelisk Blue girls' dorm.
She uses an Anti-Cure Deck, which turns life gain for her opponent into effect damage.
Voiced by: Michiko Neya (Japanese) and Veronica Taylor (English)
- Alliterative Name: Two "F" names in the dub.
- Badass Teacher: It mostly happens offscreen, but one can assume she protected Blair by holding off the Duel Ghouls until she dropped.
- Crippling Overspecialization: Her strategy is powerful, but rather flawed, as losing even one part of the combo can ruin it. Reficule is taken down easily after Jaden summons a monster that can avoid the effect of her Trap, and once she's gone, she has nothing.
- Deadly Doctor: She's the school nurse, but plays an anti-cure deck that reverses LP gain into LP loss.
- Harmful Healing: Her anti-cure deck uses Nurse Reficule the Fallen One, who can undo and reverse LP gain effects.
- Hot for Student: For Atticus. She is seen alongside most of the female students in Atticus' rabid fangirl cheering section. The first Tag Force game expands on this, as she will only agree to be the player's partner if they bring her Atticus' autograph.
- Hot Teacher: Far more to fans than she is in-universe.
- Mook Lieutenant / Elite Mook: As a Duel Ghoul she quickly gains such authority, able to control the others with ease, and while most Duel Ghouls are cut down in waves by the heroes - and never stay down long - Fontaine is a more dangerous challenge, and still doesn't stay down long.
- Our Zombies Are Different: Is turned into a Duel Zombie (or Ghoul in the English dub) during Season 3, and seems different from the others too, as she retains more articulation and speech than the others, even if it consists more of villainous banter.
Napoleon (ナポレオン) (Jean-Louis Bonaparte)
Crowler's replacement during the former's reign as Duel Academy headmaster and Marcel's dad.
He uses an (anime-only) Toy Soldier deck, whose theme is the conquests of Napoleon.
Voiced by: Naoki Tatsuta (Japanese) and Mike Pollock (English)
- And Then John Was a Zombie: Temporarily turned into a Duel Ghoul in Season 3 when duel academy was sent to the different dimension by Yubel.
- Death of a Thousand Cuts: He specializes in inflicting meager degrees of battle and effect damage in enormous quantities.
- The Dragon: To Crowler, not that he likes it much.
- Fangs Are Evil: He has quite prominent canines, and early on was portrayed as a meaner Crowler.
- Fat Bastard: He starts out as a short, chubby version of pre-Character Development Crowler.
- French Jerk: Though he does eventually lose some of the jerk.
- Gonk: Not much better than Crowler in this department. He's a short, stocky man with a puffy face that looks more than a bit like a bulldog.
- Gratuitous French: He seems to like to dip some of his sentences in it.
- Hate Sink: In Season 2. With his dickishness towards the Slifers, he pretty much takes over the spot of "punchable antagonistic character" after Crowler Took a Level in Kindness.
- HeelFace Turn: Season 3 forces him to come to terms with how much of a jerk he is. He ends up better for it.
- Jerkass: To put his jerkishness in perspective, even Crowler at his worst never tried to demolish the Red dorm.
- Jerk with a Heart of Gold: Far less than Chronos, since he's far more of an elitist, but he does genuinely care about the students of the school enough to put himself in danger to save them.
- Hidden Depths: Season 3 has him actually care about the students, mostly brought on by the presence of his son Marcel.
- Huge Girl, Tiny Guy: While only seen in shadow, his ex-wife was clearly at least two heads taller than he was.
- Living Toys: Well, virtual pseudo-life at best, but the monsters in his deck are Toy Soldiers based on the infantry of The French Revolution.
- Meaningful Name: His name, deck, and nationality are clear references to Napoléon Bonaparte.
- The Napoleon: Right down to the name. He's so short that his Duel Disk has a wheel so it won't drag across the ground while he's carrying it.
- Papa Wolf: But not as much as he'd like. He purposely isolates himself from Marcel because showing favoritism towards a student is taboo for a teacher. (And it's the hardest thing he ever had to do, as he admits.)
- Put on a Bus: Left to spend time with his son Marcel, so he was absent in season 4.
- Replacement Flat Character: He's practically Pre-Character Development Crowler in Season 2, while the latter continues to Took a Level in Kindness.
- Sadist Teacher: He loves to torment students that don't live up to his expectations.
- The Starscream: He tried to undermine Crowler and get Slifer Red torn down and turned on him at first when a job opportunity was available with Pegasus.
- Too Dumb to Live: During his duel with Crowler, he claims that he adjusted his deck and strategies to perfectly counter Ancient Gear cards, but stupidly included Negate Attack, a trap that's completely useless against most of that archetype's heavy hitters.
- Took a Level in Kindness: In season 3.
- Verbal Tic: "De aru" in the original version. He and Crowler once got into an argument ridiculing each others' tics.
Kouji Satou (佐藤浩二, Satō Kōji」) (Mr. Stein)
One of the less important teachers at duelist academy, teaching duel theory, and history. He appears in Season 3 as an associate of Viper's to stop Jaden.
He uses a Scab-Scar Knight deck based around taking control of his opponent's monsters.
Voice actor: Mitsuru Miyamoto (Japanese) and Mark Thompson (English)
- Adaptational Jerkass: In the dub, his beef with Jaden is a petty grudge and he blames Jaden for things that are his own fault, i.e. stretching himself too thin and ruining his own professional career and being a dull, uninteresting teacher. In the original, he's still misdirecting his anger, but his reason for being so spiteful is far more justified.
- Affably Evil: He never once stops being polite, even as he blames Jaden for ruining everything.
- Badass Teacher: A former pro player and he would have outright defeated Jaden if he had just attacked instead of attempting a Taking You with Me.
- Berserk Button: Being ignorant in any way is one for him, to the point wherein the analogy of two people encountering a piece of trash on the floor (the first person notice it, but didn't pick it up whereas the second one didn't pick it up since he didn't see it), he believes that the second one is the worst compared to the first one.
- Broken Pedestal: He idolized Alexis as the ideal student, but eventually found out that even she stopped attending his class.
- Career-Ending Injury: He was forced to retire from Pro Dueling after falling very ill from upholding his financial responsibilities to his family and attending night classes to earn his teaching degree.
- Creepy Monotone: At first it's almost comical, as befitting an expy of Ben Stein. But as the duel goes on and he reveals more of his motivations and personality, his incessant droning becomes far more sinister.
- Demoted to Extra: In the dub, Professor Viper takes most of Professor Stein's impact.
- Determinator: Deconstructed. He pushes his physical and mental limits to the max when making his family's financial situation better as a Pro Duelist along with juggling his academic studies for a teaching degree that he ends up so ill to the point of having to retire from Pro Dueling.
- Disney Villain Death: Falls to his death after being defeated by Jaden.
- Evil Teacher: Crosses into this when Viper seems more than willing to let Alexis drown.
- Fallen Hero: He became a pro player to protect his family, always bearing the burden of responsibility until it broke him. Represented by his ace card being a knight covered in scabs and scars.
- Jaded Washout: A rather more tragic example. The burden of his family obligations alongside his pro career caused him to literally collapse, so he had to turn to teaching instead. Then he ends up teaching a bunch of lazy students who barely listen to his lectures, which is such a depressing experience that it drives him insane. In the dub, this is changed to him being unable to handle studying for his teaching degree and a pro dueling career at the same time, and being so boring that he barely notices that he's teaching an empty classroom.
- Insane Troll Logic: His analogy of ignorance does fall within this since he believes that the first person might come back to pick it up, but the second never will, since he knows nothing of it.
- Killed Off for Real: Which, quite frankly, is unusual for this series.
- Knight of Cerebus: The duel against him sets the tone for the rest of the season and he's the first human character to specifically die. Only the sub carries this dark tone from him as Professor Viper takes most of Professor Stein's role in the dub.
- Nap-Inducing Speak: In the dub, his voice seems to have been intentionally made to sound as boring as humanly possible. Jaden falling asleep in class isn't surprising, but there's something to be said about him putting everyone else to sleep as well. For the record, even BASTION MISAWA is shown having fallen asleep and eventually stopped attending.
- No Celebrities Were Harmed: His name and soporific voice in the dub are a direct reference to Ben Stein, particularly his role as the Economics Teacher in Ferris Bueller's Day Off.
- Remember the New Guy?: Stein's existence has never even been alluded to prior to his debut, but Jaden has apparently been in his class before.
- Scars Are Forever: In a mental and figurative sense, to where his Scab Scarknight is a representation of being broken down by the responsibility he upholds prior to becoming a teacher at Duel Academia.
- Shadow Archetype: He is essentially what Jaden could have become if Jaden completely lost sight of his passion for dueling, a character arc in season four. Coincidentally, he is essentially Zane if Zane broke down instead of snapped.
- Small Role, Big Impact: He appears only in two episodes and once in a flashback yet the duel against him is what made Jaden begin to question his carefree attitude, starting to the downward spiral that led him to cross the Despair Event Horizon. Subverted in the dub where his impact is heavily reduced.
- Stern Teacher: Deconstructed, given that he takes his job of molding young minds so seriously that he seems to regard ignorance as deserving of death.
- Taking You with Me: Attempts to do this to Jaden at the end of their duel.
- "The Reason You Suck" Speech: Delivers an elaborate one to Jaden regarding his carefree attitude and his lack of consideration for the less gifted students who emulate him and the negative impact it has on their studies.
- Tranquil Fury: Despite his entire motivation being frustration and anger, he remains unshakably polite. Especially visible during his introductory scene as he announces his intention to take revenge on his students while talking as if he's giving a history lesson.
- Unwitting Pawn: He's this to Viper twice over. Viper not only intensifies his grudge against Jaden but convinces him to use the D-band, making Stein, like everyone else, little more than a living battery for his device.
- Villain Has a Point: A villain he might be, but he is right about Jaden having a negative impact on other students. Due to his apathy towards actual schoolwork and talent in dueling, other students have stopped going to class believing that they don't need to work hard to become great duelists themselves. It is downplayed given that Jaden is commonly held in contempt despite his feats so it's not that surprising that he doesn't realize he's seen as a role model.
- Villain of the Week: Essentially. He shows up for one duel against Jaden, then gets killed off.
- With Great Power Comes Great Responsibility: A rather tragic deconstructed example. He firmly believes in the idea of upholding the responsibility of financially supporting his poverty-stricken family by becoming a Pro Duelist, and at the same time, study intensively for his teaching degree at night. The overall workload and pressure he faced under those conditions have led him to become so ill that he collapses during an important duel against The D, forcing him to retire from Pro Dueling altogether and having to teach a whole class of lazy students are where he went off the deep end.
- Would Hurt a Child: He fully supports Viper's plan to have every student in Duel Academia participate in the Disclosure Duels, knowing that every one of them is at life-threatening risk. On an individual level, he personally duels Jaden with the intention to kill the latter and even attempting a Taking You with Me. Also, he has no problems with letting Viper drown Alexis in a trap after seeing surveillance footage of her willfully skipping his class.