Brazilian here and I've read the chapter like 2 weeks ago or something.
For the people curious about it, Hagimoto has been interacting with brazilians on his facebook profile for quite a long time, like the past 2 years or so, and he grew very interested in brazilian culture, and so, someone recommended him to watch "City of God" (arguably the most internationally well-known brazilian movie out there), and it left a very deep impression on him, so it was just a matter of time for him to try his hand at writing a manga set in Brazil. He's been doing A LOT of research and having information on the subjects coming directly from brazilians themselves.
About the accuracy of the setting in the manga... first of all, we need to remember Brazil is an absolute behemoth of a huge country, so a lot of regions can differ among themselves greatly. In a loose comparison, I think it's somewhat safe to compare São Paulo to New York to some degree. Huge city, the biggest one in the whole country and where the biggest things usually happen, economically. But that's not all, there are also slums in there. São Paulo slums (or "favelas") are kinda different from the ones in Rio de Janeiro, the ones that people known more about usually.
So... yeah, places like this indeed exist in Brazil. Not the entire country is like that obviously, but these places are not that uncommon either. I'm personally from Rio de Janeiro but I know plenty of people from São Paulo who said the depiction of its slums was pretty much on point, but I can see why people are reminded more of Rio's gangs reading this rather than São Paulo's. There's a saying here that "two guys on a bike" is almost guaranteed that you'll be robbed if you see them, depending on where you are and when, and this indeed happens in the chapter LMAO (I personally was never robbed like this but I've heard about people who were).
TL;DR: Yeah, the depiction was kinda accurate, even if a bit exaggerated for dramatic storytelling reasons. Take that with a grain of salt, but it isn't too far from what actually happens in favelas sometimes.