These are what we call the 'YMMV items.' Things that some people find in this work. We call them 'your mileage might vary' because not everyone sees these things in the same way. This starts discussions in the trope lists, a thing we don't want. Please use the discussion page if you'd like to discuss any of these items.
#84 Yashima and Junichi, the abused Sekirei. Remember that Sekireis, if they aren't forced by other Sekireis at the behest of their Ashikabi (Such a Higa),they will only join those they feel the greater connection to. So unless her Ashikabi was strong enough to subdue her, this means she gave herself willingly to him because he was her perfect Master. Also look ather face in chapter 25 and 26, when Junichi got angry; either she has deep self hatred and a destructive personality disorder or she loves it.
Mikogami is Obliviously Evil. He approaches the Sekirei Plan as a very exciting game, and concerns himself with things like following the rules and the best ways to keep things interesting, even if doing so puts him at a disadvantage. None of his actions violate the rules, and in fact his aggressive pursuit of new Sekirei for his collection is not only allowed, but actively endorsed by Minaka when he runs the "Green Girl" and "Final Feather" events. Furthermore, his interactions with his Sekirei and anger at the mistreatment of the East's Sekirei suggest he's a Benevolent Boss.
Awesome Music: "Change the World", the insert song that plays during Musubi's battle with Karasuba in the 2nd season finale.
Crazy Awesome: Minaka always had shades of this; his reason for creating and enforcing the Sekirei Plan is one part Science, one part Godhood and two parts for shits and giggles, but when he blows up his own building while still inside of it to make the game he was playing with Minato more interesting in the anime, he really does show his Crazy Awesome side.
Mikogami, since he's an obvious stumbling block for Akitsu joining Minato's harem. Discussions of his impending death, and Akitsu running off to join Minato's harem, occur literally almost every single chapter.
Ensemble Darkhorse: Tsukiumi tends to perform very well in popularity contests among fans of the series.
Foe Yay Shipping: Akitsu x Minato. Since she is technically Minato's enemy, this counts.
Game Breaker: Karasuba states that Miya and Yume are both this.
Growing the Beard: The series started out primarily as fanservice and comedy, but has developed into a more serious, character-driven story over time. It still delivers on the fanservice, but has a stronger focus on plot and characterization. This began with the Bridge Escape story arc, and has continued since then.
Karasuba, who aggressively pins Musubi to a wall and commands her to get stronger, with the handle of her sword poking Musubi in a very suggestive fashion. It's also implied that Yume is The Lost Lenore, in a very disturbing kind of way.
Ron the Death Eater: Musubi seems to be the least liked of all of Minato's seikirei by fanfic writers, who often give Minato literally any other Seikirei but Musubi in their new harems for him, with some stories actually having her murdered to justify her not showing up in said fanfic. The main reasons for this stem from how "obvious" it seems she'll be the "winner" of any battle for his heart, and since that presents a major stumbling block to shippers, she gets written out or is often NOT the first one to meet him so fic writers can keep Minato's options open. As for her as a character, she does tend to get seen by some a Satellite Love Interest compared to the other Sekirei (in their defense, she can be rather ditzy), so that's another reason.
Shipping Goggles: Not as many fans as Akitsu shippers, but Uzume does have her fans who want her with Minato.
Karasuba is female too. The only reason its hard to tell at times is because unlike the other women she usually doesn't go out of her way to show her femininity off in public and has a fairly gender neutral voice.
Villain Decay: Benitsubasa and Haihane suffer what is possibly the fastest villain decay in anime history, portrayed as terrifyingly powerful antagonists at the end of season one, but reduced to incompetent jokes by the start of season two.
Woobie Species: The Sekirei, as a result of being forced to participate in a "game" that forces them to find their One True Love.....and then fight to the death with the rest of their kind in the distant hope that they might be the Final One, and earn the right to remain with their Ashikabi. It becomes even more cruel, since the odds are stacked against the vast majority thanks to the Single Numbers being more powerful than normal Sekirei. This drives several pairs to attempt to escape the game, only to be hunted down and slaughtered by the Discipline Squad.