Diabolo

Seventeen years old. Youth. A magical time. All lies.

What would you do if you thought you could save someone's life?

Would you do anything it took, right up to selling your soul to the Devil?

Diabolo follows the story of Ren and Rai, two teenagers who fell into the trap of the titular Diabolo and are now blessed with immense powers of offense and defense. The cost? Well, people gifted with the powers of Diabolo start to go insane when they turn seventeen--also the time their powers manifest—and surrender their souls at eighteen. Fully aware that there's little time left in their lives and the Diabolo ensnaring teens in their poisonous contract left and right, Ren and Rai devote themselves to saving those who have fallen.

Tropes used in Diabolo include:

Abusive Parents: Once Ren's mother finally reaches her breaking point, she realizes how much Ren is beginning to look like his father. She then tries to rape him. Failing that, she sets herself on fire.
- Mio had these as well and told Ren and Rai how her parents wanted her to disappear because she was constantly ill.
Aerith and Bob: You've got your very simple Rai and Ren and Mio and then you've got the tongue-twistery generals: Nebiros, Satanachia, Sargatanas, Agliarept, Fleurety, and Lucifuge.
Alcoholic Parent: After the initial incident with Mio, Ren's mother became one of these.
Almost Kiss
Alpha Bitch: Arisa from the 'Reincarnation Ritual' storyline.
Ambiguously Gay: Rai and by that token, Nebiros as well.
Anyone Can Die
Arc Number: Seventeen is the primary one. It is the age when powers granted by the Diabolo are at their strongest and also when most users begin falling into evil. It is also only the people who are this age who are contacted by Nema to join Heaven. Eighteen serves as a minor number in that it is the age when those blessed by the Diabolo forfeit their souls (if they haven't died yet) and, as is pointed out early in the series, one of the many ways you can get eighteen is 6 + 6 + 6.
Big Damn Villains: Near the end, Fleurety, Sargatanas and Agliarept do this. AND IT IS AWESOME.
Bittersweet Ending
Blessed with Suck: Both main characters have "Ultimate Offense" and "Ultimate Defense", at the cost of their souls on their eighteenth birthdays. Ouch.
Body Horror: The climactic roof rendezvous between Nema, the Master, Rai, and Nebiros starts off normally. And then Nema and the Master's flesh starts melting off.
The Charmer: Rai has hints of this and charms a handful of ladies through the series from a young girl to one of Satan's six generals.
Cloudcuckoolander: Rei.
Cloudcuckoolander's Minder: Nana fulfills this role for Rei.
Compelling Voice: Satanachia not only is a master of this ability, but also thoroughly enjoys the inevitable outcome.
Cooldown Hug: After going to the illegal hospital, this is invoked times two. It works. But only on Ren.
Coup De Grace: Sargatanas does this to Satanachia by connecting a dimension between her hand and Satanachia's heart and crushing it. DAYUM.
Crapsack World: The first storyline is about a dead girl who was brutally raped and murdered by her boyfriend and then revived to bear a demon child. Most of the story is equally grim.
Creepy Child: Satanachia and Mio especially, once you find out what she has done.
Cursed with Awesome: The powers of Ren and Rai are either this or Blessed with Suck.
Dark Magical Girl: Fleurety
Dead All Along: This series likes this trope. Not only was Chiaki from 'Conception' murdered, but Mio from 'Omen' as well.
Dead Little Sister: Mio. Actually averted when Mio reveals herself as the Big Bad.
Deal with the Devil: The basis of the entire plot.
Downer Ending: Depends on how optimistic you are with the outcome of the story.
Despair Event Horizon: Tsukiko quietly accepting being kept as a sex pet and getting gang-banged by her roommates acts as this for Rai.
Domestic Abuser: Several characters have these in their lives, including Mio Hashiguchi (her brother), Ren (his mother), and Tsukiko (everyone).
Dude Looks Like a Lady: Rei. His first appearance has random passersby wonder what his gender was.
False Innocence Trick
Fetus Terrible: Chiaki's impregnated with one of these in 'Conception'.
Finger-Lickin' Evil: Fleurety pulls one of these in her debut after decapitating one of her bedmates.
Four Eyes, Zero Soul: Nebiros
Gorn: Hello, hospital scene!
Gratuitous Spanish: A diabolo is a child's toy. Diablo, on the other hand, is another thing entirely... However, one could always argue that Diabolo is correct, given the ending.
Heroic BSOD: Ren has one after Rai disappears.
Heterosexual Life Partners: Ren and Rai...maybe.
Hologram Projection Imperfection: Lucifuge uses a hologram which is prone to flickering when he gets angry to act in lieu of his real body.
Homeless Hero: Both Ren and Rai qualify, though Rai's been at it for longer.
Humans Are the Real Monsters: Welcome to the world of Diabolo! Most of the population seems apathetic, socially deviant, or hyper-paranoid after Nema starts broadcasting her message to seventeen year olds. The decent humans in the series can be counted on one hand.
Ill Girl: Both Mio and Kyouya.
Infant Immortality: Averted hard. A baby is thrown to its death within the first chapter, which gives you a pretty good idea how seriously the mangaka take Anyone Can Die.
In Love with Your Carnage: Satanachia, full stop. And Nebiros seems to fancy it as well.
It Got Worse: Oh, so you're doomed to lose your soul when you turn eighteen but you get super awesome powers from it, well that's not so—wait, you start to lose your mind as your powers get stronger, okay that's pretty bad, but still—you got your powers because the little girl you played with all the time was sacrificed in a demonic ritual that you were blamed for, that's kinda screwed up-- your best friend goes batshit crazy and joins the dark side, the whole country is paranoid, there's a giant Satanic cult of seventeen year olds on the rise, parents are murdering their children out of fear, and the only way to stop it is by killing not only yourself, but your best friend as well. Well fuck.
The Man Behind the Man: Mio is the Big Bad.
Meaningful Name: Tsukiko means 'moon child'. Fleurety gets her powers from the full moon.
Minor Injury Overreaction: In 'Omen' a woman is hit by a car, but only seems to have a hand injury. She immediately starts screaming for someone to call an ambulance.
Name's the Same: Mio the Dead Little Sister and Mio Hashiguchi. The other dead little sister.
Nice Job Breaking It, Hero: After meeting Rei, Rai gets horribly sick. Ren leaves to go find Nana because she knows where illegal hospitals for the homeless are. Fearing that it's a Diabolo trap, Rai chases after him and the two find the hospital staff brutally slaughtered. The smell of the blood and the sight of the mutilated bodies causes Rai to start his fall and leaves teetering on the brink of becoming Nebiros.
The Nose Knows: Rai, who is mentioned to have a good sense of smell several times. It plays a part in initiating the fall.
Off-Model: Suddenly, Rai's missing his mouth on a splash page. Which is weird, considering that it would take two artists to overlook it. (The series is drawn by a pair of manga-ka twins.)
Off with His Head: Fleurety performs one of these as her entrance to the series.
Pinky Swear: Ren and Rai share one of these in 'Awakening'. It helps Rai remember the warmth of their friendship and what he's fighting for. And later Rai goes full Nebiros and bites his pinky off.
The Promise: And it's a heavy one. Both Ren and Rai have promised to kill each other before they turn eighteen and fall to the Diabolo.
Rape as Drama: Chiaki and Tsukiko.
Red Oni, Blue Oni: Ren is red to Rai's blue.
Religion of Evil: Heaven is not only most decidedly a cult, but an interestingly high-profile one. But then again, if a bunch of seventeen year olds started murdering everyone else and committing various other felonious acts, then someone's bound to take notice.
Rich Bitch: Lucifuge acts as a male version of this.
Self-Made Orphan: Mio
Shipper on Deck: Kyouya has his moments and is the only character who really comments on Ren and Rai's interesting relationship.
Shown Their Work: While the Six Great Spirits' names and abilities may seem sort of random, further research will yield that they're all members of the six chief gods of Hell except for Nebiros, who replaces the King of Demons Asmodeus.
"Shut Up" Kiss: Ren delivers one of these to Chiaki in 'Conception'.
Someone Elses Problem: See a potential rape victim? 'Forget it. You don't want to get involved.'
Super-Powered Evil Side: Nebiros. That is all.
- Pretty much all of the Great Spirits to varying degrees.
Superpower Lottery: The six Great Spirits. Agliarept can find out any secret, Satanachia is a puppet master who is also skilled in the Compelling Voice, Sargatanas can go anywhere by connecting two dimensions, Lucifuge is a Techno Wizard, Nebiros controls premonition and pain and is the best Necromancer in Hell, and Fleurety is the immortal queen of the night.
Sweet Polly Oliver: Nana dresses as a thuggish boy at night so people don't bother her.
Sdrawkcab Name: What's Nema backwards?
Taking You with Me: Agliarept is taking the world with him, Nebiros and Ren are going down together, parents and children are committing murder-suicides across the nation... There's lots of this, especially in the final volume. Oh, and don't forget Mio.
Tear Jerker: Oh so very much.
Woobie, Destroyer of Worlds: All six of the Great Spirits.