Spoilers Ahead For Season 4 of Bungo Stray Dogs.
The Sky Casino Arc of Bungo Stray Dogs probably could have been adapted better and is undoubtedly one of the greatest victims of Season 4's pacing. However, in spite of that, Sigma, the central figure of the arc, is no less a character worth digging into, even if the anime didn't let the audience get to know him quite as long before the action started.
Episode 49 introduced audiences to Sigma, the manager of the Sky Casino, which - as the title suggests - is a floating casino outside any nation's jurisdiction, as well as a member of The Decay of Angels. In Episode 50, the Season 4 finale, titled "SKYFALL," he pulls out all the stops to prevent The Hunting Dogs and the Agency from halting his plans. But what makes Sigma interesting isn't just his attractive casino that feels straight out of a 007 film, but rather his background and the things driving him to stand in the way of the protagonists (and antagonists). Notably, it is his past, and the fact that both he and the casino he presides over, have no past to speak of.
Fyodor's Most Powerful Pawn
When Sigma is first introduced, the audience is shown what kind of leader he is when the safety and security of his casino are put at risk thanks to the investigation by Tachihara and Teruko. He's not merely concerned about the casino, but his clients as well, displaying a remarkable recollection of information about them and how best to accommodate their needs.
Just as quickly as the audience is shown this, we are hit with how Sigma reacts to all of this behind closed doors. He's nervous and nearly cracking under immense pressure, be it his part in Fyodor's plan or the encroachment of the Agency and the Hunting Dogs. And he's not merely a desperate villain getting cornered; he needs the casino.
The first big twist of the Sky Casino Arc is the reveal that the casino itself only existed after its existence was written on the page stolen from The Book. As for Sigma's part in it, Fyodor expresses that Sigma is the most capable of protecting the casino because "the most powerful man is the man who has nothing else."
At first, Fyodor bluffs that he means Sigma has amnesia, but the truth has far stronger implications. The second twist is that he was created from The Book himself, making him no different from the Casino. Fyodor's philosophy suggests that without a past to forge one's sense of self, someone given a purpose for living will do anything to protect it.
Sigma's Determination
To Sigma, the casino is the only life he has ever known, and absent of anything else to his life beyond that, it's only natural that he would want to protect what is natural to him. It makes him a profoundly fascinating character more because of what isn't written than what is, and as a result, he doesn't come off as cruel or villainous as other antagonists.
If anything, it's easy to feel for Sigma, even if he's being used as a pawn by Fyodor to spread explosive coins around the globe. He thinks little of himself, acknowledging his weaknesses and limitations, yet fearlessly faces off against Teruko despite being disadvantaged in just about every way.
Sigma's determination is defined by his will to overcome any obstacle, with his lack of a past being seen by Fyodor as him being unburdened by the humanity of others. But in retaliation, Teruko, the one who is clearly stronger, replies with her own fearless determination, one defined by a willingness to endure great pain for the sake of one's wishes.
Just as Sigma will do anything to protect the casino because his life depends on it, Teruko will put her life on the line in pursuit of crushing evil. In response to Sigma's rather traditionally heroic assertion that "there's no wall that even a mediocre man can't overcome," Teruko reminds him of the following.
The desperation of a mediocre man is indeed terrifying. But what is there beyond that?... Beyond the wall that a mediocre man overcomes with desperation is a battle against a genius who is equally desperate. A battle where desperation holds no relative value. Welcome to our world.
The last sentence in particular bites the hardest, and Teruko doesn't even realize it. This man has only existed for three years and has staked everything on a purpose given to him, so when he's convinced that he has failed, he would rather die and take her with him, even if it won't change the outcome. And it is for that reason that Atsushi trying to save Sigma is so significant.
One of Season 4's biggest themes is without a doubt determination - notably, the determination of every character to endure the storm that has rocked the foundations of the series. However, it is more than ever about what it's always been about, which is self-affirmation. Even with no past to speak of, Sigma is just as much of a victim of where they've come from.
Atsushi is an effective hero because they've come from a traumatic past that almost convinced him that he didn't deserve to live, but found the strength and allies to tell himself that he deserved to live. For Atsushi, Kyouka, Yosano, and Sigma, there is always something to live for, and they can't be so quick to give up.
While the anime could have given Sigma a bit more time in the spotlight, what remains preserved in the anime is as true to the message of the series as ever before. It will be exciting to see where he goes next and what kind of person he will choose to be, should he be allowed to be a person in the first place. For only showing up in the last two episodes of the season, Sigma really helped Bungo Stray Dogs Season 4 end on a high note.