It may sound like an odd choice of profession in a time where bullfighting is considered a cruel and old-fashioned sport, primarily for the welfare of the animals.
However, social attitudes in some parts of the Spanish province of Castellón are not as advanced as in nearby Valencia and Barcelona, and the boy is encouraged to take up this profession by his grandfather, who does not care about the controversies surrounding bullfighting.
New documentary The boy and the suit of light, which recently premiered at the Sheffield Documentary Film Festival in England, follows the boy Borha and his relationship with his grandfather Matthias over several years.
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The director Inma de Reyes, a native of the small town of Castellón de la Plane (Castellón for short), grew up next to the bullring in the center of the city and watched the bullfight on television.
At the time, however, she did not realize that her birthplace was considered the bullfighting capital of Spain.
"It's a small town where time stands still, and people do traditional jobs, fishing, working in orange fields and doing jobs related to bullfighting, and occasionally there's a traditional religious celebration. That's how I see my hometown - as a place where nothing changes. That's why I left, I didn't fit in there, I wanted to explore the world and find out who I am outside my small town.
"When I came back for filming, I began to take a deeper look at how families instill values in children and how their personalities are shaped."
When Reyes began to deal with the subject for the documentary, her mother sent her articles from local newspapers emphasizing the tradition of bullfighting, and the director thus discovered a world she "wasn't interested in" before.
"My grandfather had books and posters about bullfighting, but I thought that was a long time ago," Reyes recalls.
"I didn't know how big that culture was."
A friend of the Spanish director, who now lives in Edinburgh, the capital of Scotland, put her in touch with a bullfighting school through which she met Borja.
In practice, a bullfighter, dressed in bright and flamboyant clothing, attempts to subdue, incapacitate or kill a bull in the arena in front of an audience.
In the film, it is clear that Matias has not achieved his dream of becoming a professional bullfighter and that his wish is for his grandson to succeed in what he has not, in part because he hopes that it could help the family out of poverty.
Borha feels that his opportunities in life are limited due to his poor background and at first he puts up with his family's wishes.
Producer Aymara Rekes says that imagining yourself as a bullfighter is "romantic" and that the dream "follows Borh".
"Everybody looks at a bullfighter as someone who enjoys respect, you don't think about murder.
"As a child, he fantasizes like his family. 'Ah, he'll be there in the arena'.
"It's a show, in a way it's a real camp, you pair up and the mothers are so proud.
"But then you have to kill the bull and that's the biggest paradox."
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A 'failing' industry
Documentary The boy and the suit of light, which was filmed over five years, does not shy away from bullfighting controversies.
Borha observes how, during the bullfight, protesters storm the arena and carry banners that say "No violence".
However, for a film dealing with bullfighting, it is notable that it contains few bullfighting scenes.
That theme is in the background of a subtle story about growing up, maturing, family, and poverty.
"We knew that bullfighting couldn't be in the foreground," says Reyes.
"The story of Borha's upbringing had to be in the center of attention, partly so that viewers could enjoy the film.
"You can watch bullfights on YouTube and I didn't want to show more scenes like that.
"It's more about shaping the child's personality".
In fact, only two bullfights took place during the filming of the documentary.
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Reyes, who now lives in Edinburgh, describes Borja as "gentle and caring", and that kind of personality is probably not suited to the world of bullfighting.
"In the beginning, I was amazed by Borha's commitment, he carried out his tasks so zealously.
"He seemed to think, 'This is what I've been told to do and this is what I'm going to do.'
"I think he's an amazing kid," says Reyes.
"I hope that in the film you will see how he grows up, that he is less and less dedicated to killing the bull.
"As a director, I also felt that Borha was not made for this, and he somehow knew it.
The film shows scenes of Borja and his brother practicing using models of a bull's head mounted on a wheel, while their grandfather watches them.
He follows Borha in other situations as well - hanging out with friends and how a traditional bullfighting costume is tailored for him.
However, it was challenging to bring the story of Borja to the fore, because, like many of his peers, it was not always his job to talk about his feelings.
"During the filming, I tried to understand what Borja was thinking without saying it, because I don't think he would ever tell anyone that he wouldn't do that, but you can guess," says Reyes.
"So it was really difficult to convey the thoughts and feelings on the screen, to convey that he started to think about it without any narration or conversation with him."
She attributes the credit to her cameraman, who managed to capture Borh's feelings through facial expressions and body language.
"Just looking at it, you start to understand that there is a lot going on in Borja itself".
Although bullfighting is not illegal in Spain, many cities have introduced bans.
Bullfighting is also occasionally held in parts of Portugal, southern France, Mexico, Ecuador, Venezuela and Peru.
In many countries, including the United Kingdom, they have been banned or are in the process of making such a decision.
Colombia is gradually introducing a ban that should take effect across the country in 2027.
Reyes is aware that when they hear that the film contains bullfighting scenes, some people may not want to watch it, but she says that "the more important message of the documentary is that children should be allowed to explore and be whatever they want."
"And I also hope that it broadens [viewers'] views in the sense that you shouldn't immediately judge people for doing something that you think is bad and that they should be given a chance to explain why it's their choice.
"Not everyone has the privilege of choosing a profession or going to university, even if they live in Europe.
"I hope the bullfighting scenes won't turn people away from watching the movie."
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Rekes says bullfighting probably has no future, even for those who pursue it.
"The reality is that it's a failing industry," he says.
"It's falling apart, it doesn't exist anymore.
"People who want to keep the tradition think it's very important, but most of the bullfighters are unemployed.
"It's not what it used to be, and that's clearly visible in the film."
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