Seikon no Qwaser: Jotei no Shouzou

This episode, although it was technically taken from the manga, has major differences, even when compared to the regular anime. For starters, Ekaterina Kurae, also known as Katja, and Teresa Berea show uncharacteristically goofy faces and funny dispositions here, which never happens in the canon storyline. While easily decapitating the heads of her enemies in her calm state, in this episode, despite being very angry at the villain for saying that her chest is small multiple times over (like he is asking for it), which is, again, out of character for her, Kurae only handicaps everyone, destroying the top of the building they are in, ... like a scene straight out of a kids' show.

Moreover, Sasha has apparently become a pervert who likes to chack out big breasts for research (Jiraiya much?) by peeping on girls changing, while the Human Firecracker prefers small boobs such as his daughter's. Furthermore, they, Martyr Sasha and the Gold Qwaser's right-hand man, the Qwaser of Natrium, also known as the Phoenix of Conviction, are easily caught off guard by a boobytrap (composed of a log, similar to the one Haruno Sakura from Naruto uses in the Forest of Death) which sends the two flying to the sky in a team-Rocket fashion.

Finally, the serious religious organization from the manga is portrayed here as just a fake breasts-detox society, led by a boob-crazed failed qwaser, of which element is never revealed, and Shiizaki Ruru, Ekaterina's "smart" classmate, turns out to be a horny slut, along with her mother, wanting her own tits to be sucked again by Katja in the end.

Like the show, this episode was ruined by excessive, I will not say "fan-service," because that is fine if done right, but comedy. I recommend giving the manga more priority, since this is one of the anime that is worse on television.

The episode us refered to in the second season but this is only a side story. The thing is this episode is an outlier compared to the rest of the series.
Changes:
Ekaterina Kurae is shown as one whose has compassion for her enemies and this time instead of killing them off in a sadistic fashion, she just handicaps them. Also Ekaterina Kurae shows off a little nip which the anime and manga try to refrain from doing due to how young she looks. Then during a scene where Sasha and Otori were caught peeking at the girls while they were getting their measurements, a simple trap ... in which a log that is tied up comes down and sends them flying. Sasha and Otori should have be able to dodge them, especially Otori as he was as overpowered as they come. Basically this episode messes up the personalities of the characters quite a bit.