Given that we don't have much knowledge about this 'black shalwar story', it's hard to determine the main characters. It could be a family, where one member's black shalwar is a significant part of the family's story. Maybe there's an older woman in the family who passes down the black shalwar, and her granddaughter could be another main character as she inherits and experiences things related to the shalwar.
I'm not sure specifically what 'the black shalwar story' is about as there could be many stories with that name. It might be about a particular black shalwar (a type of traditional clothing) and an event or series of events related to it, like a mystery, a family heirloom, or a cultural significance.
The shalwar kameez for boys in the cartoon might have bright colors and unique patterns. Maybe it also has some cute detailing to make it stand out.
There's David Mason too. He's involved in many of the key events in the main story, especially those related to the future part of the plot.
Since I don't know the exact details of this story, it's hard to say for sure. But if it's related to 'Black Clover', it could feature Asta, Yuno, and their friends. They are the main characters in the original 'Black Clover' series, so it's likely they would be involved in this black beach story as well.
The main character in 'Black Beauty' is, of course, Black Beauty himself. He is a horse who narrates the story through his own experiences. Another important character is Ginger, a fellow horse who has a fiery temperament. Then there is John Manly, a kind and skilled groom who takes good care of Black Beauty and the other horses.
Since I don't know the exact 'Black Pool Story', I can't say for sure who the main characters are.
The main characters in the 'Black Morass Story' could be many things. It might be a family that has been stranded near the black morass and has to find a way out. There could be a villain who is using the inaccessibility of the black morass for his own evil purposes, like hiding something or luring people into danger. There could also be a spiritual or mythical being that is associated with the black morass, and a human character has to interact with it, either as an ally or an adversary.
Since I don't know the details of 'the black marriage story', I can't say for sure who the main characters are. They could be an ordinary black couple trying to make their marriage work.
Since I don't know the exact 'the black angel story', it's difficult to say. But likely, the black angel itself would be a main character. There might also be other characters like humans who interact with the black angel, either as friends, foes, or victims.
As I don't know the specific 'the black forest story', it's difficult to say for sure. But if it's a traditional fairy - tale - like story set in the Black Forest, there might be a young protagonist, perhaps a woodsman or a lost child. There could also be a witch or an old hermit who lives deep in the forest.