Maybe I’m crazy…

But I believe the square guard who wears black is actually the Frontman’s son. I haven’t seen anyone else say this, but it seemed kind of likely to me.

So we know the Frontman’s wife died because something was wrong with her liver. And —at least according to “Young-il”— she was pregnant. So it’s very possible that after he won the game, he came back with the money trying to save his wife, but he was too late (just like Gi-hun with his mom) and she was already dead/dying, but ended up delivering the baby.

Then where does the black square guard come in? Well he seems to act like a stand-in for the frontman, almost like he’s going to be taking over the job soon. Which would make sense if the frontman was passing it down to his son. It would be really weird for them to introduce this character solely for the frontman to play in the game, without him being someone important.

The whole organ harvesting thing in season 1 also seemed kind of random. Like I get the guards are trying to make extra money, and it getting exposed is how the idea of the games being “fair” is introduced, but it still seemed very strange.

So with the black square guard seemingly being in charge of the organ harvesting, it makes a lot more sense considering he actually has a motive. His mom dying from her liver issues, and so he believes that selling these organs could help people like her, sort of giving him a some closure or something.

Now this part I’m a little less convinced about, but I think it’s possible that number 11 (the guard) is his twin. Which is why the black square guard still protects her even when she gets in the way of the organ harvesting. And the reason she’s so against them doing that is because she thinks selling the organs is predatory to people like her mom, since they’re probably very expensive and obviously couldn’t afford it. (This also makes less sense, since why would the frontman’s son be a powerful square guard, while his daughter is just a triangle guard who has to live in her car when she’s not at the games)