Spoilers for Fate/Stay Night: Unlimited Blade Works and minor spoilers for Fate/Stay Night: Heaven's Feel.
Despite essentially being the mascot for the Fate Series, Saber (AKA Artoria Pendragon) tends to have a rough go of things depending on the story, especially in Ufotable's adaptations. She might get killed, turned evil, or kidnapped, but one sizable chunk from Unlimited Blade Works feels particularly disrespectful to the character looking back on the TV anime.
2014's Unlimited Blade Works adapts the titular second route from the hit 2004 visual novel Fate/Stay Night, the one wherein Rin Tohsaka is the main female heroine and love interest to protagonist Shirou Emiya. Each of the three routes differs in their themes, the path the hero takes, and which of the female cast - Saber, Rin, or Sakura - plays a major role as a deuteragonist. At the end of UBW's first season, Saber - who is Shirou's Servant in the Holy Grail War - is kidnapped and Shirou's status as a Master is revoked, effectively kicking him out of the war. This establishes the stakes for Season 2, as Shirou and Rin spend a great deal of time plotting to save Saber, but it's what happens to Saber during this time that feels... gross.
Because of The Implication
Caster stealing Saber was so effectively tragic at first that when audiences first witness her in captivity below the Fuyuki Church, it's a moment ripe with tonal whiplash. The proud King of Knights is seen sporting an uncharacteristic white dress and long gloves, bound by her hands. It gives a captured princess vibe which on its own clashes with Saber's aesthetic, but if that was where the description ended, there would be no real problem whatsoever.
Saber isn't merely a damsel in chains. With her hands bound, she finds herself bending over with her dress bundled up and pulled over her backside which is mercifully not shown to the audience. She also looks exhausted, but she hasn't fallen to her knees in a believable manner for one having her mana leeched from her. Instead, the unrealistic and suggestive pose forces upon the imagination the idea that Saber was being sexually assaulted by Caster.
It's a moment that is preserved from the original visual novel, but frankly, if any creative liberties were to be taken, one would argue it should have been cut completely. The whole scene would have come off as fetishistic whether the show had directly acknowledged the implication or not (for the record, they don't call attention to it through dialog).
Some will point out how Caster doing this to Saber ties into their backstory and all other manners of explanation, but no amount of context would change how out of place it feels. From the outset, UBW doesn't present itself with quite the same grim-dark tone as other works in the same universe. Garden of Sinners approaches sexual assault as well, but in a context more tonally equipped and with execution far more direct, which isn't to say that it will sit well with everyone.
UBW is way lighter compared to Gen Urobuchi's Fate/Zero which itself has its own problems with depictions of women. Here, Saber's sudden sexualization comes out of nowhere, and even if it were to be taken on its own, its execution is made worse by how completely voiceless Saber is. For five episodes, she barely utters a word in protest or shows defiance.
Practically every scene set in this basement treats Saber like a set dressing; a doll propped up or slumped down, while the other characters discuss plans. The doll metaphor feels apropos of how Caster talks to and treats Saber, but even if someone were to defend it as intentional, the issue could be argued to be just as much about a lack of commitment as it is about going over the line.
Shirou and Rin are in this basement twice and both times - including when they rescue her - it feels like Saber doesn't even exist until she's freed. It's as if, in an effort to prevent her torment from being excessive, they don't emphasize it at all, meaning the story lacks a sense of urgency about saving her.
That, combined with UBW's pacing, makes Saber's predicament feel small, which is all the more cantankerous to the story due to her unnecessary objectification. In a weird way, committing harder to the idea might have made it more effective, albeit at the risk of creating something way worse. But that also might have made it way harder to feel bad for Caster later on.
No matter how you cut it, Saber's objectification during her capture by Caster just doesn't work, at least in the anime, and that's being generous to the original source material. It could have at least been alleviated by not having the weird sex implication in Episode 13. At least in that case, Saber would have been merely underused. It's not like she's not used to it already.
The Saber Problem
Were it not for a bevy of greater scenes and the overall circumstances of the productions, one might think that Ufotable has a vendetta against Saber. Fate/Zero is great series, but the way the story treats Saber and her character is questionable and has been debated among fans for ages. Granted, this is also coming from a show that practically made a speed run out of strangling its female characters by the end, so there's more than one problem here.
With regard to Fate/Stay Night, Heaven's Feel saw Saber turn evil for two-thirds of the trilogy. The only animated adaptation of Saber's route was the Studio Deen anime and while it's good, a lot of viewers probably will be reluctant to check it out because it's not as pretty as Ufotable's work. UBW - and especially its alternate ending OVA - is the best ending Saber gets from the studio, and even then, there's this unfortunate blight in the form of her kidnapping.
It's not like the show is ruined or that it's some unforgivably offensive character assassination. It was just kinda weird and takes the viewer out of the experience. It's probably the worst thing in the anime and contributes greatly to a narrative lull that already holds the series back - and right before some of the best episodes, at that.
Fate/Stay Night: Unlimited Blade Works is a mostly faithful adaptation that some would argue wasn't quite faithful enough and for good reason. However, if the unfortunate case of Saber's kidnapping is anything to go off, not everything needs to get carried over. And besides all that, it's a reminder that it's probably time the Fate route got a remake.