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Tear Jerker: Girls und Panzer
It's not immediately obvious, but as soon as you realize up to WHICH point Maho has sacrified her own happiness for Miho's sake, you discover the poor girl's whole life has likely been a walking Tear Jerker. Then you begin to read more deeper into her lack of expression, and it starts to move into horrific territory.
The bittersweet ending of Little Army may be a Tear Jerker alone. But if you combine its aftermath (Miho following Nishizumi-style Tankery despite Maho's sacrifice) with Maho not having our viewer's knowledge of the Anime series, which means that Maho's sacrifice was apparently (for her) in vain (at least, betwen prequel and series), she becomes a failed Tragic Hero of river-overflowing proportions. Tears which she can't shed if she is to mantain her facade. That leaves us.
Arguably, the real point at which Maho's plan fails is when Shiho announces her intention to disown Miho for not being a good Nishizumi, meaning that even if Maho is the heiress, Miho is still forced to live by her mother's rules. At that point, she abandons part of her facade, and actually begins expressing her opinion about Miho in front of their mother; one can only imagine what she's actually feeling.
In Chapter 6 of the Little Army manga, Miho and Maho's mother arrives, and Miho watches her sister go into full Ice Queen mode (particularly when she confirms Emi's accusation and coldly asks "Was that all you wanted to talk about?"). Given that previous chapters and flashbacks had indicated that Miho greatly admired Maho, and a flashback shows her going into tankery because of Maho, she's devastated as a result.
Chapter 12 of the main series manga portrays the scene in which Oarai is given three hours to surrender to Pravda, but with a cruel twist in that adaptation. In this version, it's indicated that Miho knows that if she doesn't win here, she will be disinherited, and yet outwardly, she is no less certain of her initial decision to surrender and avoid the possibility of her friends being injured in the skirmish. Yukari, the only one there who knows about the personal stakes for Miho, finds it almost unbearable having to watch Miho make this decision.
Yukari: (thinking) Mi... Miss Nishizumi...! Why!? Just why Miss Nishizumi! Accepted your disinheritance? Are you fine with just that!?