ATU510A, better known as Cinderella, is one of the most widely distributed fairy tales in the world. It exists on every continent among a majority of disparate cultures, from the ancient world to modern retellings. (Its lesser-known counterpart, Donkeyskin [ATU510B], also enjoys widespread distribution.) For many modern readers, its popularity hinges on the fantasy of being whisked away from a terrible life to a good one, but if you dig deeper into the tale type, it's not about a passive princess being rescued. It's about a young woman realizing that she's worth something and taking steps to get herself out of a bad situation. The prince is a means to an end, not the prize.

Betrothed to My Sister's Ex is a mix of modern views of Cinderella with the other reading about a girl who pulls herself out of a bad situation. Although on the surface it looks a lot like Marie is simply being rescued by Kyros, the story is equally about her recognizing that she's worth something, framing Kyros as both Prince Charming and Fairy Godmother. While Marie's journey to understanding that she has value can feel a little much at times, ultimately the story is about finding the courage to take what you deserve – and to give back to others what they deserve.

The story follows Marie Shaderan, the middle child of a minor noble family. Marie may be the biological child of her parents, but that doesn't stop them from treating her like a servant – her anxiety and red hair combine to make them despise her, with her mother repeatedly damning her as “unlucky” or “cursed” because of her coloring. They relegate the running of the estate to Marie and force her to sleep in a garden shed while lavishing affection on her older sister Anastasia and younger brother Cedric. They even go so far as to have a ball on Marie's birthday, not for Marie, but to find Anastasia a husband. They're definitely on display in the Anime Hall of Terrible Parents.

But they can't stop Marie from meeting Kyros Granado, a much higher-ranked noble. Kyros falls hard for Marie, both her looks and her obvious intelligence, and he quickly sends a letter proposing…to Anastasia, due to a mix-up. A miserable Anastasia is packed off to the wedding, but dies on the way in an accident, and Marie is sent as a “replacement” for her sister. Canny viewers will note the old “if there's no corpse, there is no death” trope at play, which in no way detracts from Marie's journey to believing that she's worth just as much as her sister as a human being.

It's not an easy realization. While Kyros's almost insane devotion to her is played for laughs (and he is funny), the story is mostly about people overcoming the odds that others have imposed upon them. Marie's issues are multifaceted: she has no idea how smart she is or that men might find her attractive, and she doesn't believe she deserves anything good. Kyros, meanwhile, has grown up experiencing prejudice due to his biracial heritage and the fact that his mother, Liu-Liu, was not his father's first (legal) wife. He's used to being wanted for his money and position, and what draws him to Marie is that she doesn't care about those things. Meanwhile, Anastasia is burdened by her parents' expectations that she will be their perfect doll of a daughter, completely disregarding what she wants or that she's a person with her own will. While not all of these plotlines are given equal space in the series – Marie's take precedent – having them all there is important, because it shows that there's a pattern: of abuse in Marie and Anastasia's household and of systemic racism in the kingdom in general. It's not a political statement to say that those two elements drive the characters' actions and beliefs, making them more grounded than sometimes happens in fantasy works.

Although there are plenty of predictable plot points in the series, what makes it work is Marie's consistent growth. It may take her most of the twelve episodes to realize that Kyros truly loves her and that she's allowed to be happy, but she does show progress throughout, and it moves at a believable pace – it's a two steps forward, one step back situation. Supporting characters aren't just there for color, with Mio – Kyros' friend and employee – being the standout. Mio is, quite frankly, the best character in the series, pulling strings both behind and before the scenes, taking no garbage from anyone, and making sure that things are moving in the right direction. She's a force of nature and easily one of the best characters of the show, if not the year.

Art and animation are a bit more mixed. For some reason, someone decided that Marie's red hair should be outlined in electric lime at all times, and that absolutely does not work. But real effort is made to show how she looks with and without makeup in a more realistic way than we often get. Animation can be stiff and awkward, and then suddenly whip out some of the only correct ballroom dancing in a non-ballroom anime I've seen. It's vastly uneven. Fortunately, the voice cast is much more so, and special mention goes to Ryōhei Kimura's smarmy, smug Prince Louisphon.

Betrothed to My Sister's Ex isn't a perfect show, but it's still a good one. Spinning off of multiple Cinderella variants, it uses folkloric elements in a distinctly anime way, even taking care to make sure that the villains of the piece are understandable, even if they are cartoonish. Marie deserves to go to the ball – and this series allows her to come to that realization with a little help from her prince.