As Alina Gray revels in the chaos Touka and Nemu have resumed (and paints a picture of it) and Yachiyo chases after Embryo Eye, Kyuubey calmly waxes philosophic about how he’s actually doing magical girls a favor, since their sacrifice is a small price to pay for, ya know, extending the life of the universe.
He also goes on about how “what is right” depends entirely on when you live in human history. In some times “justice” hast meant protecting the weak; in some times it has meant eliminating them to make humanity stronger.
Those lofty areas of rumination are of no interest to Iroha, who is now safely within Little Kyuubey, which means she finally gets to reunite with Ui. Her goal is to get out of there with Ui, but Ui tells her it’s too late for that. However bad a big sister Iroha believes herself to be, Ui believes she’s been a worse little sister.
She’s not herself anymore, and hasn’t been since she became a magical girl with Touka and Nemu. Unlike those two, Ui is content to admit they failed and gracefully back away (and say what you want about Kyuubey’s designs, the plan ws and is short-sighted at best).
Ui tells Iroha they must part, because while her story is over, Iroha still has a lot of people left to save, starting with Kuroe. Iroha breaks Iroha out of Little Kyuubey just when Kuroe’s doppel is overwhelming her. But while Iroha wants to save Kuroe, Kuroe doesn’t want to be saved, because she doesn’t believe she’s worth saving.
We finally learn why (or at least part of why) Kuroe feels that way. Whether she became a magical girl because Iroha did or for some other reason is not clear. However, once she became one, she was weak, and barely able to scrape by. But just as there’s always a bigger fish in the sea, there’s always a weaker magical girl.
When Kuroe meets one who is stuck in a witch’s labyrinth, she rescues her and the stray cat she meant to save. We never see this magical girl’s eyes or learn her name (nor does Kuroe). But when the girl asked for a spare grief seed, Kuroe lied and said she didn’t have one, when in reality she did have one to keep her above water.
Kuroe believes the choice she made back then was no choice at all. She went so far as to save that girl, only to abandon her to a longer, slower death. She has no idea what happened to her, but it’s likely to have been nothing good, considering her Soul Gem was already in bad shape.
So now, having had to say goodbye to her dear little sister, Iroha now finds herself trying to convince her friend that she can and should be saved. Kuroe is far from keen on the idea, especially as her darker side replaces that mystery girl with Iroha in her mind, thus upping her guilt and despair.
While she’s under the heavy emotional influence of her downer doppel, Kuroe decides she’ll make it so that she doesn’t have to save anyone and doesn’t need to be saved. Her doppel breaks through Alina’s barrier and she transforms into a full-on witch, Iroha watching helplessly as Kuroe’s blackened vestigial human body is torn to pieces.
As the witch soars out of earth’s atmosphere, likely up to no good at all, Iroha’s defeated face turns to one of grim duty and determination. If she couldn’t save Kuroe, she’ll at least put her out of her misery, and spare a great number of lives she’d claim as a witch. Three episodes into this four-part finale, I earnestly hope we’ve reached the lowest depths, and that Iroha and her remaining friends can soon begin to ascend from the shadows.