It'd be easy enough to peg Index as a conventional action series, for the very simple reason that it is a conventional action series. It likes conventions. In any given arc there's generally a villain and a damsel in distress and of course a hero: Toma, an ordinary guy with one extraordinary power and a total inability to abide injustice. The hero is always the underdog and always makes a spectacular comeback. The damsels fall for the hero, and occasionally end up living with him as well. It is essentially just another shonen action show. And that's just fine. After all, if it wasn't conventional, it couldn't be proof of how good conventional anime can be. Index doesn't work because it's new or unique; it works because it's, well, good.

There are three complete arcs in this section of the series: the first one six episodes, the second three, and the third five. The first sets the basic template in that it revolves around Toma rescuing a girl from evil forces and is wholly self-contained. It also sets the tone in that from its first scene, wherein Toma intervenes between a girl and a gang of punks to save the punks, to its last, in which it brings all six episodes of Index and Toma's relationship to bear in one heartbreaking exchange, it does pretty much everything right. If there's something to be done to make the story's essentially familiar arc engrossing and exciting, the show does it. The events he is embroiled in are big and complicated and only ever partially visible. His rapport with Index is instantaneous, utterly adorable, and under constant threat of obliteration. Toma's enemies have giant self-regenerating fire beasts, godly sword skills, and mind-hijacking tapestries of defensive magic cast on the girl he loves. Toma has a magic-cancelling right hand and a mean right straight. The fights are a little lopsided to say the least. Toma must marshal every ounce of will and skill he has—including surprising rhetorical skills and a facility for sudden sideways leaps of logic—to come out on top. When the arc truly draws everything together, as it does in the end, when one of those sideways leaps of logic ends an unbearable emotional conundrum with a satisfyingly logical plot twist (and a spectacular magic battle), it's a thrill on every relevant level: emotional, mental, and visceral.

At half the number of episodes, the next arc has a hard time matching that. The girl this time has pretty much zero connection to Toma and is significantly less interesting as well. There are few complexities of plot, setting, or character. The enemy is a single, flawed man rather than a heartless worldwide organization. The situation is clear-cut and the thrust of the arc short and straightforward: just a girl trapped in a tower by an evil magician, in need of rescuing by a couple of heroes. To balance things out the show spends some time parsing the consequences of the previous arc's shocker ending and ultimately ties Index into the villain's scheme (and back-story). Eventually it builds its own head of steam, mostly thanks to the unbearable yet seemingly indestructible villain and Toma's clever method of dispatching him. (How do you destroy a man who can make any thought into reality? Make him think something that's to your advantage.) It also has a cruel streak—flaying and dismemberment play crucial roles—which carries over into the next arc.

The third arc takes that cruelty and runs with it, devising an experiment in which thousands of innocent girls are manufactured and slaughtered in the back alleys of Academy City in the name of science. It has the further advantage of returning the series to the science side of its premise, and of using an established character—Mikoto, the girl Toma briefly rescues the punks from—to deliver its emotional punch. It's the most cleanly and smoothly constructed of the arcs, slowly revealing the extent of the evil being perpetrated and the stakes if the evil continues, and moving with inexorable inevitability towards Toma's showdown with the untouchable psychopath at its center. The showdown is a stunner too: smart, scary, spectacularly destructive, and so very satisfying in its conclusion. (How do you destroy a man who's so powerful that he's never been so much as touched? Beat the holy sh** out of him of course.)

Returning to the science side of the show's science-meets-magic premise is an advantage mostly because spell-casting can be a little unsatisfying as action goes. That's particularly true in the opening arc, where flame-beasts and magical energy cannons are the weapons of choice. Mind you, they're dazzling cannon blasts and seriously Satanic flame beasts. But they still lack visceral impact. The fights get their power mostly from the characters, their emotions, and the stakes involved; not from the visuals. That's less so for the sword fight, which is one mean dose of scenery-dicing showboating, and for the second arc's finale, which prominently features very physical threats like guns and flying, arm-lopping knives. It's Toma's battle with arc three's Accelerator, however, that really demonstrates director Hiroshi Nishikiori's action chops. It takes its share of shortcuts—the series, though active and attractive, is rarely without them—but also delivers the kind of cogently arranged fist-to-the-face violence that magic generally precludes. Toma and Accelerator rush and spar as I-beams hurtle and buildings shatter and rails bend and strike like lethal metal snakes and, of course, bad guys get pummeled in glorious detail.

Outside of action, Nishikiori gives the series a curiously alienated, isolating feel. For all its size and technological advancement, Academy City seems rather a creepy and lonely place. It has something to do with the lack of people—a great deal of it takes place at night, but even in the daytime the streets seem deserted—and something to do with the neon haze that the city is perpetually draped in. The city looks as if it's enveloped in a people-repelling spell, even when it isn't. When Toma is out and about, he seems very much alone. Which is entirely appropriate. Characters for their part look great, with iconic combinations of clothing and coloration—especially Index's silver hair and safety-pinned white nun's habit—and a wide variety of well-rendered expressions (angry Toma is an entirely different person from everyday Toma). I've's score, by the way, is a rocking, electronics-laden treat that isn't deployed so much as desperately reined in to prevent it from chewing the show to shreds.

If there is a truly damaging criticism to be leveled at Index, it's that it's less than optimally paced. The series sails by when an arc is underway, comes shuddering to a halt whenever one ends, and then dashes off again when a new one starts, giving the plot an odd herky-jerky motion. It's best to watch the arcs in isolation—as they were intended; it's based off of a series of light novels after all—and pay close attention while things are in motion: important nuances are easily lost if you don't keep a sharp eye out. Do that, though, and you won't be disappointed. Many series shoot for Index's mixture of action, drama, comedy and (yes) romance; very few actually hit it. Even fewer hit it this hard.