The title of this short story is a tongue-in-cheek nod to one of its key themes: darkness and light, both literal and metaphorical. At the end of the story, the narrator, Bana, explains the "joke" inherent in the title. He says that Africa is the "Dark Continent" because it smothers its own light, with the light, or "suns," in this case, meaning its good men. 

"Sun" is, of course, a homophone of "son," and Bana makes clear in his story that he believes he and his two colleagues are some of the most "honest" sons of Africa, despite being "bandits." While many people behave in criminal ways, only Bana and his colleagues are honest about it, allowing them to be "perspicacious" and "light" of heart and conscience. 

My heart is light as the daylight which seeps stealthily into our dark cell.

Everybody else is still willingly living in darkness. 

The narrator contrasts the literal darkness of his prison cell with the metaphorical darkness of the wider nation and continent. Ultimately, he believes that the "ignorance" in which his prison guard, a representation of a menial corrupt worker, is living is more of an entrapment than his literal imprisonment. 

While Bana and his friends might be trapped in the darkness waiting to be freed, the morning will eventually rise again and bring freedom with it, even though that freedom will bring death. The prison guard, however, will still exist in an "unfeeling" nation that is "inured to evil," so the light will not enter his life. He will remain in the darkness. 

There are several references to religion and martyrdom in this piece. The positioning of Bana as an honest man awaiting his punishment for being honest brings to mind the story of Socrates, or perhaps even Jesus. This might be implied in Bana's observation that "the cock crows now," as dawn comes. 

In the Bible, Jesus tells his disciple Peter that he will "deny him" before the cock crows, so the crowing of the cock makes Peter realize that he has indeed denied Jesus, symbolizing the beginning of the end. As an honest man, Jesus will be crucified; likewise, in this story, the crowing of the cock indicates that Bana's death will come soon. It is inevitable. 

Bana knows that a priest will come to him and his friends before his death to ask whether they have "any last wishes." However, Bana says he will call the priest a "hypocrite" and tell him to go to hell. The priest is simply another puppet of a regime of "miserable wretches," and Bana suggests that it is the living the priest should be praying for. 

Everyone except Bana and his friends are the ones who will be forced to continue to exist in an "evil" world. Bana and his friends will soon be leaving it. Death is the only way, at the moment, for them to escape a hypocritical world that views them as villains, even though they are morally upright in their own way. 

It's the guard and you the living who are in prison, the ultimate prison from which you cannot escape because you do not know that you are incarcerated.

Throughout the story, Bana repeatedly questions what moral code it is that will condemn him and his friends while celebrating others who are equally corrupt. He points out that "robbery is the base line" for many in this nation and that the only difference between himself and a Government official who has stolen money is that Bana has been honest about it. Everything in...

The idea of legacy is crucial to this story, whose title is what Bana hopes will be his epitaph. While much of the letter Bana writes is to "unburden" himself, he specifies early on that the primary reason he is writing is to "ask a small favor" of Zole. Near the end of the story, it is revealed that this favor is for Zole to commission a statue of Bana and then arrange for a grave. 

Bana hopes that he will be remembered after death -- perhaps his death will have more hope of bringing about change than any of his actions in life, even from the moment the news appears in the paper. 

I should find myself recorded in the annals of our history. A history of violence, of murder, of disregard for life.

Bana's legacy will live on in other ways. He is sure that "the High Court Judge himself will never forget" the action he and his colleagues took to demand the death sentence immediately for their crime. Bana's honesty represents a diversion from what the Judge usually witnesses under a corrupt government: self-serving hypocrisy. The impact of it will linger in the mind of those who witnessed it. 

Bana also mourns the fact that "Sazan and Jimba will die unsung": 

Sazan and Jimba will have left nothing behind. I shall leave at least this letter, which, please, keep for posterity.

However, as he extols the virtues of his friends in his letter, Bana is ensuring in some small way that this is not the case. Anyone who reads Bana's letter will remember Sazan and Jimba too.