It's directed by Akitarou Daichi, so I was guaranteed to watch it sooner or later. This was his debut as a series director, though, and he doesn't think it's one of his better works. It also got cancelled despite good viewing figures, because it hadn't caught its target audience and wasn't selling enough tie-in merchandise. (Its timeslot was filled for the next three weeks with "specials" comprised of footage from the associated stage musical. These broke my brain and I'd advise avoiding them.)
It's a 1990s fighting magical girl series, i.e. back in the day of Sailor Moon (the good adaptation). Ririka is a 10-year-old girl who's asked to be a magical girl called Nurse Angel and fight evil. She said "yes" because the boy who asked is tall and handsome and she's got a huge crush on him. (He's an alien called Kanou. Ririka also has a likeable childhood friend called Seiya.) So far, so formulaic. Monsters of the week? Yup. A distant, unreachable magical kingdom ruled by a queen who'll turn out to have a mystical link with Ririka? You bet. Love interests and a bitchy school rival who also fancies Kanou? Inevitably.
Frankly, the first dozen episodes are soporific. Perfectly good children's TV and sometimes funny, but nothing remarkable. They're capable of being mildly sinister (e.g. ep.7 with a memory vampire and "did Ririka just kill that baddie?"). Kanou can erase people's memories. Also, there's an evil duplicate Kanou in ep.9 who made Misaki so cross that she stood up and wagged a finger at the screen.
Then, though, the gloves come off. Of all things, I was reminded of Buffy Season 2 (which this pre-dated). The story arc beats are similar, including equivalents of Angel, Buffy, Xander and Spike. There's nothing as shattering as the Buffy Season 2 finale, but they're willing to kill regular cast members who'd have plot immunity even in much harder-edged shows. (Also like Buffy, death isn't necessarily permanent, but it's still shocking when it happens.) Then, later, the series left my mental map and also introduced a sort of Dawn. (Except that this one's funnier.)
The show's usually fluffy. It's a likeable children's anime with a sense of humour. (Akitarou Daichi's not yet on full blast, but his timing's already good and he has some inspired moments. Look out for the Valentine's Day background gags in ep.31, for instance. Poor Duey.) Ririka's a sweetheart and you'll be cheering for Seiya. I watched this show with my son (aged 9) and my daughter (aged 5) and they were pretty much the target audience. Nonetheless, good characters can become bad and vice-versa. The story arc baddie is a Saturday morning cartoon figure, but occasionally his evil is shocking, e.g. how he handles his minion in ep.19.
Then there's the bittersweet series ending. I'd heard about this. I was wondering if they'd really dare to go that far. How would Natsuki and Misaki react? Answer: there's an epilogue that makes it all okay, but any children who turned off the TV too early will have been traumatised. That's also the show's most Daichi-esque episode, because it demonstrates his mastery of tone. Unbelievable. That birthday party. The silliness and the genuinely funny gags, but the show's eleven-year-old heroine is getting sent to her death. And it works. The wildly clashing elements make each other stronger. Welcome to the director of Kodocha.
You could call this the first magical girl genre deconstruction, a decade before anyone else. It's not a Dark Magical Girl show, c.f. Puella Magi Madoka Magica, but it's subverting genre tropes in a way that's not true of other magical girl shows that happened to get dark on occasion, like Sailor Moon, the stronger PreCure instalments and even Magical Princess Minky Momo.
Imagine this show as having three seasons. Season 1 (the first third) is unremarkable. Season 2 is a fluffy anime version of Buffy Season 2. Season 3 then introduces a new comedy regular (who's great) and seems to be setting off in a whole new direction until the show's sponsors bring down the axe prematurely. But that finale is what had always been planned.
It looks like fluff for girls and an adult viewer's attention might wander a bit in the early episodes. It is, though, a show that can be likened seriously to Buffy. Sometimes its handling of equivalent story elements is more interesting.