Usual disclaimer - there may be a few minor spoilers below, but I won't spoil anything major. Also, I assume that the reader is familiar with the basics of the series.
The Sekirei series, in general, has caused me a lot of thought recently. I've read almost every review that I could find online about both seasons of the show, and it really strikes me as a microcosm of the larger issues that surround ecchi anime series. The producers of the series have clearly decided to market this show as something akin to a Skinemax movie - there's a ton of nudity and in-your-face fanservice, although no outright sexual content. And that turns a lot of people off. The problem is that Sekirei has a genuinely strong story behind it, and a cast of endearing characters.
There's a scene in one of the early episodes of the first season of Sekirei that, to me, serves as an allegory for the series as a whole. Musubi takes Minato's hand and places it on her breast, asking him to feel how fast her heart is beating - the scene is shown in the anime as part fanservice, part comedy (putting Minato in an uncomfortable situation). But it really is a simple way of looking at this series - underneath the breasts and awkward situations lies a warm, beating heart. And that's the one thing that Sekirei has more of than any other anime (and most American tv shows) that I've seen - lots of heart. It's a tender, charming series if you're able to get past the glaring fanservice. Some can and some can't, and that's just the life of an ecchi show.
STORY - 8.5/10
The story in Sekirei - Pure Engagement kicks up a notch action-wise from the first season. There are two major arcs present - one involving Homura and one involving Uzume and her Ashikabi. Additionally, Minato expands his group of Sekirei.
As I mentioned in my Sekirei review, this is one of the few series where I have read the manga. And for whatever reason, the producers of the anime decided to drastically change the plot from the manga once they entered the Uzume storyline. It's a decision that has evoked much disdain from fans of the manga, and it definitely causes the plot to enter more cliche territory (complete with a tower dungeon crawl over the last two episodes) than the source material intended. But I think that it's executed well, and it still fits within the context of the overall Sekirei Plan. I'm generally a person who hates when TV/movies/whatever take a good book and alter it dramatically - it never ends up being as good as the book. But that doesn't mean that it can't still be good, just not as good.
Sekirei - Pure Engagement still presents the dual personality of the series, where it isn't sure if it wants to be an ecchi comedy or a serious story that happens to have some fanservice. This series is always going to have the scenes where the girls feel the need to have their serious conversations while all naked in the bath, and that's just something that you have to roll with if you watch this series. But I think that they've done a bit better job of balancing the harem concepts with the more serious tones of the overall plot in this season.
The show also delves into some good weighty ideas once the Sekirei Plan reaches its next phase. Minato's sister (and, inadvertantly, Tsuikiumi) encoutner an Ashikabi who abuses his Sekirei, and you realize that not everyone gets to be lovey-dovey with their Sekirei. There are men (or women, I guess, although most Ashikabi seem to be men) out there who will take advantage of the submissive nature of the Sekirei pact. The series also goes a bit farther in driving home the idea that, eventually, all but one of the Sekirei must be defeated - there's a particularly heart-wrenching scene where (again) Minato's sister and her Sekirei defeat another Sekirei, only to have the opposing Ashikabi break down crying as he holds the limp body of the girl that he loves.
Lastly, quite a bit more background is given about the early days of the Sekirei, immediately after their discovery. To me, these scenes are hugely interesting, and really serve to tie in what's going on in the present to the larger themes that exist in the series.
ANIMATION - 7.5/10
My biggest gripe with the series remains the animation choice to supplant what could be serious emotional scenes with the use of chibi-esque character models and over-the-top reactions. This is probably the biggest area where the slightly more serious tone of the manga gets lost, and while the character development in this show goes well beyond the girls' chests, this animation choice doesn't help.
Sekirei - Pure Engagement still looks beautiful, and they've cleaned up the issues with the oddly-shaped characters that popped up now and then in the first season.
SOUND - 9/10
As with the first season, the voice acting in the English dub is excellent. This goes hand-in-hand with the Characters section below, but I'm a huge proponent that strong voice acting adds a layer of depth to the characters that can't be achieved otherwise.
The score is always fitting, and the opening and closing themes are appropriately touching.
CHARACTERS - 8/10
Sekirei - Pure Engagement takes another step in identifying the characters beyond their simple archetypes. There will always be an element of the shy, oblivious male lead in any harem show, but Minato isn't as oblivious as most. In fact, I think Minato's character works so well because he seems to genuinely care about people (whether they're his Sekireis or not) so much. Each of the characters in the show is charming in their own way.
Each of the Sekirei in Minato's group bring something unique to the table, and their interactions with one another, and with Minato himself, create diverse and intertwined relationships. There are a number of touching character moments, for almost all of the characters, mixed in with the action and fanservice of the series.
We get some newcomers to Minato's group (one of which is easily predictable from the end of last season), and we also meet Uzume's Ashikabi. Some of the secondary characters are fleshed out a bit more, but with so many characters to keep track of, there isn't a ton of focus outside of Minato's group and his sister and her Sekirei.
OVERALL - 8.5/10
I covered most of this in the introduction, but my impression of this series is that at its core it's about a group of characters who care for one another (whether they admit it or not) and are trying to do what they can to thwart to psychotic plans of an evil genius. Minato is the link that ties everyone together in these efforts. The boobs and harem scenes and elaborate fight sequences are all entertaining in their own way, but are really peripheral to the heart of the series.
I don't want to spoil anything major, but I will say that episode 10 really touches on what this series is all about - it goes way beyond the superficiality of fanservice or Sekirei battles. And even in the most heartfelt scene of that episode, when Minato is leaning over one of the girls, in a truly emotional exchange, there's a giant boob and half-covered nipple taking up a large portion of the lower left-hand corner of the screen. And such is the Sekirei series - a big helping of heart, with a healthy side order of boobs.