It's a bog-standard battle harem. Our protagonist is a token male in an otherwise all-female world where they fight monsters. The manga's fans think Season 1 is mediocre and has worse animation and storytelling than Season 2, but frankly I saw little difference between them. Season 2 has more serious battles and badass villains, but I never took it seriously. No one dies, you never believe the characters are truly in danger and the battles lack tension.

At least I watched it, though. I don't plan ever to watch the author's famously dark earlier series, Akame ga Kill!, which I understand is just murder, murder, murder.

The show wastes interesting potential. Its world is a matriarchy, because only girls can gain superpowers. Gender equality doesn't exist. Men have lower status and are denied the privileges of the stronger sex. The show has an entire alternate history... which gets ignored in favour of cool fights and fanservice. Almost everything that happens is in an alternate dimension with no men except Yuuki, so gender relations don't exist because all the relationships are "Yuuki and yet another girl". They're all perfectly nice and will do naughty things with him. (Well, except the 11-year-old. Mercifully, the show keeps her out of all that.) Furthermore, the Anti-Demon Corps is a military organisation, so all the relationships are ostensibly based in military rank. The girls are his superiors. They call him "slave", but this doesn't mean anything.

The battles, monster-killing, etc. are fine. It's anime nonsense, but it's okay and it carries the series. It's less memorable than the fanservice, but you can't run 24 episodes successfully on fanservice alone.

So, this fanservice. Yuuki can transform into monster forms for use in battle, but the price is some kind of vaguely lewd "reward". There's nudity and nipples on the Blu-rays. This is above average for fanservice battle harem anime, which rarely justify their sleaze. Here, the naughty silliness is part of the plot. There's a reason for it. The girls never know will be required on any occasion and might be taken aback, which gives the scenes characterisation and dramatic purpose. (Nothing like that can be said of the communal bath scenes, but hey.) If you watch this show, those "rewards" will be the only thing you'll remember even one month later. Everything else, nope. It's too generic. The fanservice, though, has personality and occasionally even manages to be sexy in a way that's not just tits and arse.

That's why I prefer Season 1. The show's not yet taking its basics for granted. It's exploring its ideas and playing with them in a way that's less true later. In Season 2, the naughty rewards have settled into a routine that never surprises anyone. The result is sleaze that can feel dumber and more try-hard.

I quite like the cast. Yuuki's a milquetoast harem protagonist, but he's also a nice guy who works hard, doesn't drool over the girls and takes his "caretaker" job seriously. As for the girls, they're no better than "okay", but they serve their function in the show and carry the episodes. Size-Changing Girl is probably the most memorable, because of her superpower.

The best I'd say about this show is that it's watchable. It doesn't take itself too seriously, it has fun with its ideas and its protagonist isn't a spotlight hog. On the contrary, he's the lowest-status cast member. It's the girls who are in charge of the fighting. Yuuki's just support. The show's also reasonably well-paced and doesn't go berserk with power-ups. It's a lot like Infinite Stratos, but better.

The show's fans disagree with me, though. I've seen them say that Season 1 needs a remake and that Season 2 is a huge improvement. Crumbs. I imagine they're judging it as a battle anime, which wouldn't have occurred to me.