- The Ace: On tests. He's always been at the top of his class.
- Agent Scully: Continues to make mundane explanations for events even when it's patently obvious what's going on.
- Blue Blood
- The Complainer Is Always Wrong
- Generation Xerox: He looks just like Solomon, even though they're separated by thousands of years he's a very distant relative.
- Genre Blindness: Even in the title "devils and realist".
- Glory Hound
- Grade Skipper
- Green Eyes
- Guile Hero: He's not above bribing and blackmailing his rivals to get ahead. Tests and grades are another story though.
- No Sell: His skepticism ultimately proves to be more useful than it appears and makes him immune to ecstasy.
- Power Nullifier: He can negate the power of any of the 72 pillars of Solomon just by saying it out loud.
- The Protagonist
- Science Hero
- Skepticism Failure: William continues to disbelieve in demons even when they're appearing out of nowhere in front of him and fighting with supernatural powers.
- Teen Genius: He apparently understands the frontiers of science in his day and constantly brings up complex equations and name drops famous scientists.
SolomonThe mythical king of millennia past.
- Brilliant but Lazy: Didn't have any interest in pursuing power and occupied himself with books instead.
- The Dreaded: Feared by both demons and humans.
- Green Eyes
- Hair Decorations
- Hikikomori as lampshaded by Dantalion himself,
- —>Dantalion: "How a Hikikomori like you could be the wisest man is a mystery!"
- MacGuffin: His spirit is somehow linked to his ring.
- Neet: Before he went and became king.
- Perpetual Smiler
- Story-Breaker Power
- This is a human who could smack a demon king around without a sweat, and slaughtering an army while he was at it without lifting a finger
IsaacWilliam's best friend at school. Isaac could do better on grades, but he makes up for it in expertise about the paranormal, much to William's chagrin. Isaac is cheerful and optimistic, contrasting William's deadpan realism.
- Agent Mulder
- Bumbling Sidekick: Only in academics.
- Crouching Moron, Hidden Badass: He beats William easily during their magic training.
- Curtains Match the Window
- Geek: For magic, religion, and history.
- Mr. Exposition: Because of his extensive knowledge of religious and supernatural things, Isaac gets to fill William in on anything weird that appears.
- Plucky Comic Relief
Samuel Liddell Mathers
William Wynn Westcott
Kevin CecilThe real Kevin. He used to work for the Twinings but left years ago. Now he works as a lawyer in a different town and met William again for the first time in years when "Kevin" took William out on holiday. He is considerate toward William and invites him to go to him if he ever has trouble.
"Kevin" aka UrielOur hero's faithful house steward. He is level-headed and responsible, aside from his gambling problem. Kevin's family has a long tradition of serving the Twinings and Kevin himself has been more or less a Parental Substitute for William ever since his parents' deaths, and he has no intention of breaking it even though William has gone broke. Recently he has come to William's school as the replacement campus priest. It has been revealed that Kevin is actually Uriel, a former archangel and currently keeping watch over Solomon's reincarnation. With another reveal, it turns out that the real Kevin left the Twinings long ago and is now working as a successful lawyer. After William found out, his relationship with "Kevin" has become strained.
- Badass Preacher
- Barrier Warrior
- Battle Butler
- Beauty Equals Goodness
- Becoming the Mask: He genuinely cares about William, which makes his duties to Heaven that much harder.
- Bolt of Divine Retribution: His weapon of choice.
- Broken Angel
- Broken Bird: Got one of his wings torn off by Michael and stripped of his rank sometime in the past.
- Curtains Match The Windows
- Extreme Doormat
- Good Is Not Soft: Just try messing with William.
- Guardian Angel
- Keigo: Is always very polite.
- Kindly House Steward
- Man in White
- Nice Guy: Unfortunately for him.
- Names to Run Away From Really Fast : Uriel, the angel of repentance and cruelty.
- While every angels appeared in this series seems to be the bad guy, ironically Uriel is the only one very well known by demons as a sadist.
- Perpetual Molt: One of the first clues that he's not what he appears to be. Of course, that's if you've never watched the Spoiler Opening.
- Purple Eyes
- Apparently in the series, Isaac the resident occult geek could find 'sadist' written under his description from certain book.
- Stepford Smiler: As "Kevin".
- Submissive Badass
- Took a Level in Kindness: Compare Solomon-era Uriel to William-era Uriel.
- The Atoner: The reason he is loyal to William at first is because he want to be forgiven for what he had done in the past to Solomon.
"Elliot Eden" aka MichaelThe highest of the archangels, Michael is the "one who is like God" and has an ego to match. He supervises Uriel's work and threatens to tear off his remaining wing if he fails to secure Solomon's soul for Heaven.
- A God Am I
- Axe Crazy
- Bad Boss
- Bitch in Sheep's Clothing
- The Bully: To Uriel. He's always taunting him, telling him he looks down on him (because he doesn't consider him an angel anymore), and beating him.
- Does Not Like Shoes
- Evil Albino
- Foot Focus
- Freudian Excuse: Apparently Lucifer's falling affected him greatly and even now the only thing he thinks about is capturing his brother. Michael hasn't rested for years and it's taking a toll on his mind and body.
- "Just Joking" Justification: He has a habit of saying terrible things to people, then smiling and saying, "just kidding".
- Proud Warrior Race Guy
- Red Eyes, Take Warning
Joan of ArcMichael's protegee. She was brought to heaven by Michael after her execution and has become a Saint and fearsome warrior in Michael's army. She has the potential to become an archangel sometime in the future.
- Action Girl
- Axe Crazy: Has no problem with slaughtering demons.
- Brainwashed and Crazy: According to the demons.
- Church Militant
- Hellish Pupils
- Improbable Weapon: Wields a flag.
- Magical Girl: Basically.
- Purity Personified: So much that even being in Hell weakens her.
- Virgin Power : She lampshade this herself.
RaguelUriel's helper. He cares greatly for his master's well being and will do anything for him.
- My Master, Right or Wrong
- Submissive Badass
- Suspiciously Similar Substitute: William mistakes him for Kevin on first glance when Raguel is serving at a party.
- Well-Intentioned Extremist: He urges Uriel to raise William to heaven because the consequences of doing otherwise would put him in danger.
"Sean Christian" aka MetatronChief of the Virtues.
SandalphonMetatron's younger brother.
ZacharielMaster of the Dominions.
RazielChief of the Powers.
RaphaelChief of the Ophanim.
DantalionHe was the first demon to be befriended by Solomon and the first demon to approach William in this life. He is the 71st pillar of Solomon and a Duke who commands the 36th army of Hell. He is one of the candidates to become the next Emperor after Lucifer and wants William to elect him. When he fails initially, he becomes a student at William's school to stay close to him and convince him to pick him as successor.
- Badass Cape
- Berserk Button: Talking about his past before he became a nephilim.
- Dark Is Not Evil: Even though he's a demon, he doesn't really do anything bad unwarranted onscreen. On the other hand, it is said that he killed hundreds back in the day in order to gain power.
- Hot as Hell
- Offscreen Villainy
- Red Eyes, Take Warning
- Tall, Dark and Handsome
SytryThe second candidate to approach William, Sytry is the "beautiful doll" of Baalberith and Solomon's 12th pillar. Sytry first wanted William to elect him as successor, but as he spent more time with him he began to care about him as a person and not just as Solomon's successor. Now Sytry wants William to choose him so he would have a reason to protect him from both Heaven and Hell.
- Attractive Bent-Gender: One of the reason's he's so popular.
- Curtains Match The Windows: Both purple.
- Dude Looks Like a Lady: William even calls him androgynous.
- Hair Decorations: In his demon form. He also magically accumulates them from his fan club at school.
- Instant Fanclub: His has over 200 members.
- Spell My Name with an "S": Sytry, Sitri.
- Sweet Tooth: Is usually shown eating cookies or candy. In the cooking competition, he chose Dantalion's servant over his own because his servant didn't make a dessert.
- Tomboyish Sidetails
- Wholesome Crossdresser
"Nathan Caxton" aka CamioThe secret identity of the head boy at school. He is calm and collected as well as one of the most powerful demons in hell. He is the third candidate introduced thus far and is the protegee of Beelzebub. He has been in love with the house mother at school ever since they first met decades ago.Unlike other candidates he never ask William to elect him and strangely uncomfortable when his reason is questioned. It's implied he agree to be nominated so he has reason to protect William.
- All of the Other Reindeer: Implied to be part of his tragic past, lampshaded by Camio himself.
- Camio— "My demon blood prevents me from truly living as a human and my human half leave me no place in hell."
- Always Someone Better: To William, preventing him from having the top grades in his class.
- Berserk Button: Camio doesn't like to be reminded that he is a Halfling.
- Classical Music: He's apparently good enough at piano that Beelzebub compared Mozart to him back in the day.
- Death Glare: While it took a lot on Sytry and Dantalion to intercept an army of demon, all Camio need are a well placed ultimatum and this to send them running back to demon world.
- Half-Human Hybrid
- he is the illegitimate child of Lucifer and princess of Troy
- Interspecies Romance
- Multicolored Hair: Greenish blue and silver.
- Starcrossed Lovers
- Stoic Spectacles
- Sugar and Ice Personality
- When He Smiles
Gilles de Rais
- Agent Peacock
- Camp Straight: Dresses in a way that makes him look androgynous and fully intends on defiling Joan of Arc in every way imaginable.
AstarothSouthern King of Hell.
- Aloof Dark-Haired Girl
- Ambiguously Brown
- Lady of War: While she hasn't been shown in combat yet, with her military inspired outfits and giant warship, she certainly gives off this impression.
- Mama Bear
- Ms. Fanservice: To balance out the huge amount of Bishounen, she frequently appears lounging in the bathtub. Also, her outfits can be pretty Stripperiffic.
- Supernatural Gold Eyes
- Precocious Crush: She insists she's Dantalion's fiance.
BeelzebubNorthern King of Hell, known as Lord of Flies. He is also ex-husband of Astaroth and father of Lamia. He is Camio's mentor who nominate him.
BaalberithWestern King of Hell, and Lord of Spider. He is also Sytry's uncle and mentor.
- The Starscream: Wants Solomon's Ring so he can rule Hell and overthrow Lucifer. He also implies he plans on using it as a way to get back into Heaven.
- The Chessmaster
SamaelEastern King of Hell.
- Eyepatch of Power
- Horned Humanoid
- Absolute Loyalty: To Lucifer, so much that it's implied he didn't nominate or support any candidate because of this.
John DeeCamio's butler
- Historical-Domain Character: From real John Dee.
- Heterosexual Life-Partners: After his human death he become Camio's sole household member.