It's an old saying that you can choose your friends but not your family. But what do you do when your family steals your friends? That's the situation Ichika finds herself in as part of her isekai experience, and not necessarily in the way you're thinking. (Or would be thinking, had you not read the title of the series.) Since high school, Ichika, now a pre-med college student, has been seeing a boy named Cecil through an old hand mirror. Although the picture was fuzzy, his voice came through loud and clear, and the two formed a solid friendship, although Cecil also developed romantic feelings for the older Ichika. Ichika told her sister Karen, her elder by one year, all about Cecil, something which comes back to bite her when both Karen and the hand mirror vanish one day. Bereft at the dual losses of sister and friend, Ichika tries her best to carry on…and then one year later, the mirror reappears, pulling Ichika through it.

Happy reunions, however, are not the stock-in-trade of this series. Ichika is quickly spotted by a very familiar woman, who runs up to her, joyously calling her "Karen." While Ichika is stunned, her sister turns to a grown-up Cecil and introduces him to "her older sister Karen." When Cecil calls her "Ichika," the real Ichika realizes that something has gone very wrong, and not just with the timeline. (That's later explained as one of the odd effects of world-crossing; timelines rarely line up.) It turns out that the older sister she adored was never who Ichika thought she was, and she's getting some hard lessons in a reality she never wanted.

In Another World, My Sister Stole My Name is a bit of a spin on the traditional villainess isekai story. Karen is plainly a villainess, and her every action is centered on herself and making sure that she, and she alone, gets what she wants. When she fell through the mirror and realized that the Cecil her younger sister blabbered on about was a handsome prince, she immediately began using the stories Ichika told her to convince him that she was the girl he fell in love with, and she's not pleased that the real Ichika has shown up. Her plan to make the best of it thus far only involves keeping Cecil and Ichika apart and marrying Ichika off to Cecil's brother Noah, but it's not hard to imagine her taking things further if she feels she needs to. The story does a good job of showing Karen's ruthless interior lurking just below the surface, and it seems very plausible that if push came to shove, she'd resort to crueler or more drastic measures to remove her little sister.

Fortunately for Ichika, she may not be as smart as she thinks she is. Cecil, who of course can't be fully isolated from the real Ichika, makes some remarks about how he wishes that her sister was more like her, with the implication that he's noticed that his fiancée isn't the woman he knew before. There are also a few hints that Cecil may not be entirely who Ichika thought he was, and the strained relationship between him and Noah feels more significant than it appears. Is Karen not the only one lying about her identity? She's been able to pull off her deception because the mirror's image wasn't clear, so it seems possible that that would go both ways. Noah's certainly bitter about something, and his personality doesn't make it seem like it's just whoever the heir and the spare is. There's a lot of intrigue here, even as Ichika is making an honest attempt to just live her best life, while always keeping the thought of finding a way back to her world in the corner of her mind.

Ichika being a bright person, both in terms of intelligence and personality, helps to keep the book from feeling bleak. She's upset about the situation, especially as it pertains to Karen's treatment of her, which has gone so far as to order that Ichika not be taught magic in order to solidify her own position, but she's also not just going to sit back and take it. She studies, she learns, and she thinks, which may turn out to be the most important thing. She's trying to sort through her own emotions as she goes, with the primary hurt being that it turns out that she didn't really know her sister at all. Although the text doesn't harp on it, that still emerges as the worst part of the entire experience for Ichika. It's a betrayal of her entire life up to this point, and she's struggling to cope with it.

In Another World, My Sister Stole My Name is a nice twist to the typical isekai villainess story. Karen's villainy isn't overwrought and Ichika is very sympathetic while not feeling like a limp dishrag of a character. The art is very pretty, detailed without being overwhelming, and defaulting to a pseudo-Victorian look for backgrounds and costumes. With a not-entirely-unexpected twist at the end of the volume and some major questions about the princes still dangling, this feels like the start of a series it will be easy to get hooked on.