Anyway, Shakugan no Shana was the other Kugimiya Rei anime I watched recently and I also enjoyed it, probably more than ZnT. While SnS had the same staring seiyu as ZnT, the story was a less campy and more serious which I felt brought about a better performance overall. The basic plot runs like this. There's another world filled with, well, 'demons' for the lack of a better word. The demons can cross over to our world and basically end up eating the life force of normal everyday people in order to accumulate power for themselves. This power of existence can be used to cast normally impossible spells or fuel normal abilities/provide healing. Some of the demon lords actually have a conscience however and try to stop those of their own kind who go marauding. In order to accomplish this they grant some of their power to human beings, making them Flame Hazes, a sort of hybrid whose job it is to run around the human world and destroy the interlopers. In addition to fighting off these invaders, the Flame Hazes are also responsible for lessening the negative impact of having people consumed. They create a 'torch' when someone is eaten, which is sort of a remnant of a person powered by a little life energy. Over time the energy is expended and the torch goes poof. This makes sure that you don't have huge groups of people all going pop at once, which could threaten the fabric of existence. Instead the damage is spread out and while all of those people are in effect dead, their torch lives on for a time and then vanishes on its own.
As the story opens our protagonist Yuji, a normal highschool student, has an unfortunate encounter with a couple of demon monsters who begin eating people. He's saved by Shana, a flame haze, but discovers that he's already dead. At some point in the past he was already 'eaten' and became a torch. Seeing as the supernatural world views torches mostly as leftover flotsam, Yuji doesn't exactly get a warm reception. He pretty much assumes that he'll go poof any day, like any other torch, but it turns out that he's lucky. Some torches have treasure hidden inside them. I know, I found this idea sort of whacky too. I guess it's like RPGs where when you kill a monster an unexpected item pops out. Anyway, he just happens to have the Reiji Maigo (Midnight Lost Child) inside him, which happens to be one of the greatest artifacts ever created and which refreshes his power of existence each day at midnight. That means that unless he somehow uses up all of his power of existence before midnight, he should continue to survive indefinitely unlike other torches. As the story develops, he wins Shana over with his determination to make something of himself despite his limitations. He goes through training to develop his abilities and joins with Shana and diverse others to fight off the legions who would love to slice him open and scoop out the Reiji Maigo inside.
In the end, SnS is a mixture of action drama and school life comedy. Yuji continues to attend school and Shana soon joins him there, taking over the identity of another student who had been a torch which extinguished. Add in Kazumi, a female classmate who is in love with Yuji and you have a classic love triangle to boot. The episodes alternate between stretches where the biggest plot twist is whether Shana can actually learn to cook without poisoning someone and finally make a bento for Yuji to an invasion by hostile forces of demons trying to accomplish a centuries old Xanatos gambit to rule the world. It's not a bad mix though there are plenty of times when you're hoping for one type of episode and run into a streak of the other. I thought for sure the second season was going to feature a lot more action and plot advancement and instead ran headlong into episode after episode of Slice of Life. That said, it was still an enjoyable watch overall and I'm thinking about reading the manga, which explores the plot in greater depth. While only touched upon partially, it turns out that the Reiji Maigo has multiple existences trapped inside it, one of which is some uber-powerful psycho nutjob which I believe eventually emerges and takes over Yuji to some degree. There are also a multitude of factions and a pretty intricate backstory for which you only get drips and drabs of in the anime. Until I work my way through the manga I won't know if the anime skimmed off the cream and left the dross behind or if there are still diamonds in the rough left undiscovered.
Oh, and I almost forgot to mention it but the Title line is Shana's catch phrase in the anime. It basically translates to Shut up Shut up Shut up! She is considered one of the great tsundere characters of all time after all. It wouldn't make sense for her catch phrase to be all peaches and cream right off the bat. You have to work you way up to that level.