This review is separated into 2 sections: a spoilers-free review for new readers of the series, and a more critical analysis for those who has read or seen Kakegurui (main story) before, containing minor spoilers. Feel free to scroll down and find the one you're looking for.
(I am currently caught up to all 52 chapters of Twin I have access to, as of Jan 27 2020.)
Synopsis, in case you missed it:
Kakegurui Twin tells the story of Saotome Mary, an intelligent scholarship student, and her path to achieving success at Hyakkaou Private Academy, a school which evaluates people by their ability to gamble, and attended by
students who are much richer than her. The stronger you are at gambling, the higher your social status would be in the academy. After learning what brutality the system may bring, Saotome sets off to quite literally, gamble her way to victory, making friends and enemies along her exciting journey.
>> The following section is for readers with no prior experience with Kakegurui (main story), and does not contain any spoilers.
Although Kakegurui Twin is the prequel to Kakegurui (main story), I would highly recommend starting the series with Kakegurui the manga (ongoing) or the Kakegurui anime (2 seasons aired, 12 episodes each). Not only was Kekegurui published first, reading/watching that first would give you a better beginners' perspective to the universe, and a greater appreciation for the Twin prequel. Case in point, Saotome Mary (main character in Twin) is the second female lead in the main story, and the consequences of gambling can be better understood by reading Twin's "predecessor". That being said, Twin still provides adequate introduction to its unique premise and fascinating system, one of compulsive gambling and class divide.
Story-wise, character chemistry and the specially designed games for gambling are some of the strongest suit the Kakegurui series (as a whole) has to offer. Saotome is one of my favorite characters of all time, so I would be lying if I say I'm reading Twin because of something else other than her. With her being the main character of this series, it wouldn't take much else for me to enjoy Twin. If you enjoy stories with a strong, confident, tsundere (but not the irritating type) female leading protagonist, Saotome Mary will not disappoint you. It is a bit unfair to compare the rest of the cast with her, as they were given much less "screen time", while some have much less impact to the story's progression as a whole. However, their design, both aesthetically and characteristically (personality and back stories) are highly memorable. Instead of diving deep into their past, Twin spends more time displaying their growth and change of attitude caused by character interaction and gambling, and I found that really enjoyable. Using this formula, story progression feels smooth and satisfying, with very little filler in between. The more I read, the more I get this "as long as the characters are interacting I don't really mind what they're actually doing" vibe, if you know what I mean :)
Some may point out that most side characters have extreme and unrelatable traits, to which I very much agree with. I don't think that makes them bad characters. With a setting as ridiculous (in a good way) as a "school for rich teenagers to gamble at", it's reasonable that the characters are just as twisted. This to me makes for a more riveting story.
Much like the main Kakegurui story, Twin also offers plenty of interesting setups, challenges, and rivals for Saotome to go against. These people don't gamble for fun, but usually for a deeper, sometimes more sinister purpose. Since money isn't usually the only thing on the line, the gambles have higher risks than regular casino games. Strategies and cheats are always applicable, even if the game itself seemed entirely luck based. Twin never cease to deliver new and creative games with their respective twists, and special risks and incentives tailored for each setting. Each game is drastically different from one another, keeping it fresh every time. The rules to each game are made clear to readers, so are the reactions of the players during the gamble. Their strategies are later revealed, allowing readers to strategize or theorize beforehand. All these elements combined adds an extra element of thrill to the games. If you enjoy table top games, or the likes of No Game No Life and Akagi, you will likely enjoy both Kakegurui and Twin.
As much as I'd like to say that both character and story are flawless, Twin has its fair share of issues. In terms of characters, the protagonists have somewhat heavy plot armor, and Saotome is a bit "overpowered". In terms of plot, the outcomes of the gambles have been really predictable, and some risks and the associate rewards of certain games feel non-existent. However, I'd like to point out that the outcome of a prequel is drastically restrained by the sequel, which serves as a reason behind some of the problems mentioned.
TLDR: It is important to read or see Kakegurui first before approaching Kakegurui Twin. Twin itself is really entertaining, but if you're looking for something else other than entertainment, please look elsewhere.
-------------------------------------------------- Spoilers ahead! --------------------------------------------------
>> The following section is for readers who has seen/read a fair amount of Kakegurui (main story), and contains minor spoilers for both series.
(I am currently caught up to all 71 chapters of Kakegurui both season of anime, as of Jan 27 2020.)
Let me just get the elephants out of the room.
1. The majority of the new characters in Twin are absent in the main story. Some felt so important to Mary, I simply couldn't imagine how this prequel being wrapped up within the short time frame (1 year) without conflicting with the main story. That is unless all the new characters introduced in Twin just graduated, or magically disappeared. If the characters in Twin were alluded to in the main story, this would not have been as jarring.
2. I hate to say it, but Mary can't really function as the lead character in a prequal of Kakegurui. In the main story, Mary takes on a redemption arc because of how she treated Suzui Ryouta and Yumeko. Twin however disputes the idea that Mary would gamble with Yumeko in the first place, because her sense of justice would not allow for it. The only other reason for Mary to do so, if not because she was a bit of a jerk, can only be out of jealousy (something to do with Suzui Ryouta), which also doesn’t fit the Mary in Twin… And then there’s the unavoidable plot armour for obvious reasons… I digress.
3. If the prequel was dated back when Kirari challenged the previous student council president, or even way back when the academy tradition of gambling had come to be, it would have been so much more interesting. Twin just felt like a missed opportunity.
Yes, the whole Twin story is kind of misplaced. It feels more like a weird ”what if Yumeko doesn’t exist and Mary was born a year earlier” spinoff than it is a simple prequel, but it really couldn’t stand on its own without the main story, so it exists as this awkward spinoff-prequel-hybrid that the writer probably did not intend for it to be.
BUT I still think Twin is wroth reading. Here’s why.
To me Kakegurui (main story) and Kakegurui Twin serve very different purposes and contribute differently to their shared universe. The main story has its spotlight on Yumeko, how her appearance has brought change to the academy (anime season 1) and the Momobami Clan (speculation) through the stage that is Hyakkaou Private Academy. The story is character (Yumeko) driven, and the events are happening because of Yumeko's unstoppable lust for gambling.
Twin however had greater emphasis on world building, and showcases the slightly more "common" side of school life at the Academy. The risks are much less extreme, with some gambles I'd consider trivial compared to ones in the main story. It isn't about Mary climbing to the very top, but rather a demonstration of how hard it is to achieve and maintain a successful school life, when you have the slightest bit of ambition while striving to be something beyond ordinary. Twin is, with a lack of a better word, environment driven, where Mary is dragged into chaos by the people around her. This helps to establish a couple things:
1. The universe when Yumeko isn't in the picture
2. The hopes and goals of students other than the cast from the main story (since Yumeko is a bit of an oddity and she tends to attract other characters with special cases)
3. How some of the regular events in normal schools operate under Hyakkaou Private Academy (monitor election, clubs and societies, festivals etc.)
4. How awesome Mary really is (which is somewhat relevant to chapter 71 of the main story manga)
There are major differences between the content as well. The main story has been building more and more suspense towards not only the outcome of gambles, but also a likely reveal of what the mysterious Momobami Clan entails. Yumeko has a clear goal in mind (to beat Kirari), and actively put herself up for various challenges including her going against student council members and the Momobami Clan members along the way. Each arc is clearly divided (as do the 2 seasons of anime). On top of that, the gambles are distinctively themed (fear, trust, compromise, determination, deception etc.), especially for the election arc.
On the other hand, Twin feels like a shorter and more lighthearted series where suspense is almost immediately resolved after each gamble. Problem appears, gamble, problem solved, rinse and repeat. Since Mary isn't really in the driving seat most of the time, the plot progression feels much more passive, and there isn’t any clear-cut arcs. I got smaller doses of satisfaction reading Twin than I did with reading the main story. But then again we should be reminded that there are plenty of limitations to what a “prequel” can deliver, as it has to be canon to the events merely a year later (hopefully so).
With all the flaws in mind, I still very much enjoyed reading Twin, even though it is structurally and thematically weaker than the main story. I get to see familiar faces from the main story, alongside elements that can't really be looked into in the main story because of where Kakegurui is heading towards. I doubt people who disliked the main story would consider reading Twin either, so there is no reason not to read Twin if you're coming from the main story, given that you can overcome the elephants previously mentioned.
If you're concerned that the art style of Twin would deviate from Kakegurui because of different illustrators, you shouldn't be. The art style had stayed consistent and good, both manga series has nailed the facial expressions that Kakegurui is known for. If I had to nitpick any noticeable differences, it would be how the panel layout of the main story felt a bit more dynamic. Literally had to flip through books of both series to spot that.
TLDR: Twin doesn't take away anything from the main story, nor does it add much to it either. You won't miss out on anything important, but why not give it a shot?
My overall rating is 7.5, for "absolutely worth my time, very fun to read, but some parts could be done better".