WAVE OF HATRED!!! and other fun facts~
Time to expound a bit on demons and the origins of their powers! Ready? AWESOME!
Basically, Viento and Potamos use their powers with the aid of something called a Wave of Hatred (if you think in terms of radiation waves, it'll hurt a little less, trust me). What this means, in layman's terms, is that their super-special-awesome-chocolatey-fudge-coated powers of AWESOME are drawn from the power of hatred. How does that even work?
Viento, like other demons, generates and uses his own wave - basically, you could refer back to Domon Kashuu and take all of his pain, anger, etc, for a demonic version of a Shining Finger. SERIOUSLY, THOUGH, one of two things generally triggers Yousuke's transformation into Viento in both the anime and manga - either he gets angry enough to produce his wave (ala The Hulk) or another demon stops by and donates/drops some wave on him.
Unlike angels, demons can not only use their own wave, they can transfer it to and from humans and one another. Early in the series, Jama-P is seen spreading a wave among the attendants at a wedding hall and Aquelda hands out hate-possessing tickets. Later in the series, we see familiars that can transform love waves into hate (although I'm assuming this isn't a power they all possess, since no one else really does this) and that can suck the hatred out of humans, once generated. Lastly, there's Katushya, who is sent to revive Viento - it's basically her job to give Yousuke Evil!Steroids until he turns into Viento.
While the absence of an innate Love Wave will weaken and eventually drain an angel (aforementioned love-wave-transforming demon hits Momoko with his vaccum ray - yeah, I know - and she goes down in an ep), the same is not true of a demon and their Hate Wave. A demon can go without their hatred entirely for years - as evidenced by both Uragano and Yousuke living normal human lives (no one ever said they wouldn't be dysfunctional). Jama-P and Potamos are also purified - instead of disappearing into the Wild Blue Yonder, they give up their evil ways and live as a... yellow... puffball... thing and a normal girl, respectively (anime only l-lol).
The downside to this is that, you guessed it, the demon will not have the same level of power. Which is not to say they're powerless entirely - Yousuke forms barriers in times of great distress and for no other reason than to protect Momoko at certain points throughout the series (in the manga, it seems they're formed more out of anger, less so in the anime). In the next-to-last episode of the anime, he even pulls that neat "I'ma generate enormous power with MAH LOVE" trick you just saw Friday! No, I can't really explain it either, except that all devils likely possess SOME inherent power, which is magnified greatly by their negative emotions.
Finally, Uragano's speech in the anime seems to hint at that possibility as well, stating that before Reine Devilla came along, the Demon World was composed of several different tribes, each leaving the others alone, and that power was the ultimate means of authority. The Rafaal, Yousuke's folks, were pretty much the top o' the heap l-lol. From this, it seems like the demons were more likely just indigenous Japanese-style water, rock, fire, and wind spirits (fun fact: each demon belongs to one of those four elements. Yes, even the ones shaped like alarm clocks and soccer balls) that were inundated with Reine Devilla's abundant Wave of Hatred.
Which just goes to show that Hell hath no fury like a woman scorned. L-LOL CLICHES.
Basically, Viento and Potamos use their powers with the aid of something called a Wave of Hatred (if you think in terms of radiation waves, it'll hurt a little less, trust me). What this means, in layman's terms, is that their super-special-awesome-chocolatey-fudge-coated powers of AWESOME are drawn from the power of hatred. How does that even work?
Viento, like other demons, generates and uses his own wave - basically, you could refer back to Domon Kashuu and take all of his pain, anger, etc, for a demonic version of a Shining Finger. SERIOUSLY, THOUGH, one of two things generally triggers Yousuke's transformation into Viento in both the anime and manga - either he gets angry enough to produce his wave (ala The Hulk) or another demon stops by and donates/drops some wave on him.
Unlike angels, demons can not only use their own wave, they can transfer it to and from humans and one another. Early in the series, Jama-P is seen spreading a wave among the attendants at a wedding hall and Aquelda hands out hate-possessing tickets. Later in the series, we see familiars that can transform love waves into hate (although I'm assuming this isn't a power they all possess, since no one else really does this) and that can suck the hatred out of humans, once generated. Lastly, there's Katushya, who is sent to revive Viento - it's basically her job to give Yousuke Evil!Steroids until he turns into Viento.
While the absence of an innate Love Wave will weaken and eventually drain an angel (aforementioned love-wave-transforming demon hits Momoko with his vaccum ray - yeah, I know - and she goes down in an ep), the same is not true of a demon and their Hate Wave. A demon can go without their hatred entirely for years - as evidenced by both Uragano and Yousuke living normal human lives (no one ever said they wouldn't be dysfunctional). Jama-P and Potamos are also purified - instead of disappearing into the Wild Blue Yonder, they give up their evil ways and live as a... yellow... puffball... thing and a normal girl, respectively (anime only l-lol).
The downside to this is that, you guessed it, the demon will not have the same level of power. Which is not to say they're powerless entirely - Yousuke forms barriers in times of great distress and for no other reason than to protect Momoko at certain points throughout the series (in the manga, it seems they're formed more out of anger, less so in the anime). In the next-to-last episode of the anime, he even pulls that neat "I'ma generate enormous power with MAH LOVE" trick you just saw Friday! No, I can't really explain it either, except that all devils likely possess SOME inherent power, which is magnified greatly by their negative emotions.
Finally, Uragano's speech in the anime seems to hint at that possibility as well, stating that before Reine Devilla came along, the Demon World was composed of several different tribes, each leaving the others alone, and that power was the ultimate means of authority. The Rafaal, Yousuke's folks, were pretty much the top o' the heap l-lol. From this, it seems like the demons were more likely just indigenous Japanese-style water, rock, fire, and wind spirits (fun fact: each demon belongs to one of those four elements. Yes, even the ones shaped like alarm clocks and soccer balls) that were inundated with Reine Devilla's abundant Wave of Hatred.
Which just goes to show that Hell hath no fury like a woman scorned. L-LOL CLICHES.