Uh... I missed it. Although I've seen around 30 eps subbed. Not sure if I should be admitting that. <_<
Hmm... I think it's like every 200 years, 500 years, something like that, a hundred demons are sent to Earth to find human partners and fight in a competition to determine the next ruler of Hell. For some reason a lot of the demons resemble small children (ask Bernie) although that's not always the case.
So you've got your human-demon pairs, with the human wielding the spellbook and calling out spells to trigger the demon's attacks. Whenever the bond between the human and demon strengthens, a new spell appears in the spellbook, essentially "leveling up" the demon. That's it in a nutshell.
It's fucking goofy to the extreme, and while I can't vouch for the dub, the Japanese VAs can be hysterical at times. On the flip side, the show can get a little too sentimental now and then, which adds to the whole "I can't believe I'm watching this" factor.
Anyway, you could say it's relatively popular, with around 18 manga volumes and close to 100 anime episodes so far. You can chell out the trailer for the second movie
here...
Now I'm kind of craving it. There's this one character who's supposed to be an international singing sensation, although all his songs are either about how great he is or how much he loves squeezing tits. I'm guessing that'll hit the cutting room floor on Toonami.