Every time Angella Okutoyi steps on court, she thinks of how tennis will change her family's life.

Raised by Mary, who works as a school cleaner in Nairobi, Okutoyi calls her grandmother 'mum'.

"She had to take of care everything by herself and she stood in as our father, mother and grandmother," Okutoyi told BBC Sport Africa.

"Tennis will help me get my grandmother from where she is now, remove her from poverty and build her a house and get her a good life.

"My grandmother is the one who pushes me to do what I am doing so seeing her happy makes me happy."

Okutoyi is already showing promise in her fledgling career, becoming the first Kenyan female to win a junior Grand Slam match as she progressed to the third round of the girls' singles at the Australian Open in January.

Mary smiles with pride in her tiny living room when she is shown pictures of Okutoyi in action in Melbourne, and it is easy to see why tennis is more than a sport for the teenager.

"I wouldn't say it's therapy but on court I know it's something that is going to help me in future," Okutoyi said.

"Tennis means everything to me because it gives us the meal that we have at home now. It gives me the courage, it helps my family."

Okutoyi is the top-ranked African in the International Tennis Federation (ITF) junior world rankings at 59 and could be a future African queen of tennis.

The Australian Open provided the chance to mix with some of her idols - but the competition itself provided a steep learning curve.

"I met some big players like Coco Gauff and Madison Keys but stepping on the court, it was a different feeling," she said.

"My main goal was to go there and enjoy every single thing I was doing and I took that through in a positive way,

"One lesson I learnt is you have to be mentally strong. We all know how to play tennis - but if you are not mentally strong or physically fit you cannot win any match there."

A fighter who 'doesn't give up'

Inspired by the great Serena Williams, Okutoyi's route from a poor background into elite tennis has not been easy.

"My daughter died during surgery when giving birth to Angella and her twin sister Rosie," Mary told BBC Sport Africa while showing us a photo of her late daughter, who was also called Angella.

"They never saw their mother."

Four years after her birth, Okutoyi started playing tennis at the Loreto Convent Valley Road school in the Kenyan capital Nairobi.

"When I was young it wasn't easy to get things," she said.

"Some days I would go to training without eating anything. Tennis wasn't easy at first. I was wearing torn shoes and I didn't have most of the equipment that I have now."

Mary and Okutoyi's uncle Allen have been part of her journey from the onset.

"I have tried my best to help her in tennis," Mary said. "We would go pick playing kit for five shillings (three pence) or 10 shillings at the market.

"We used to walk to take her to tennis matches To places like JD Tennis Academy or in [Nairobi suburb] Parklands. There is nowhere we didn't go."

Joe Karanja, a tennis instructor at Loreto Convent Valley Road, identified Angella when she was just four.

"Angella is a girl who fights, who doesn't give up," Karanja told BBC Sport Africa.

"By the time she was six, she was defeating kids of eight. When she was eight, she was defeating kids of 10, even 11. I knew she was going to go places.

"I see her playing in the senior Grand Slams. She is not far from there."

Trophies, fashion ambitions and financing questions

Aged 10, Okutoyi joined the ITF centre in Burundi on a scholarship, which was a dream come true for her grandmother.

Okutoyi has also never looked back - with her trophy cabinet filling up along the way.

"There are so many things I won; the Under-14 African Championship in 2018 in Algeria, and that same year I won the Kenya Open - the youngest to win it.

"This is my favourite one," she said showing us the African Under-18 trophy she won last year in Algeria. "This is the one that gave me the opportunity to go to the Australian Open."

Okutoyi trains on the dusty public service tennis courts in Nairobi, easily hitting balls and occasionally taking breaks to sip water and tie her blue-braided hair.

"One thing I love about the sport is that it teaches you to be independent," she said. "It takes determination, discipline and belief."

She sees her forehand as her strength, but Tennis Kenya secretary general Wanjiru Mbugua Karani warns Okutoyi will need financial support to continue to compete and turn professional.

"Now Angella needs a lot of travelling to get a lot of ranking points," Mbugua Karani said.

"Without this travelling, then players are not be able to turn pro. So yes, it gets more and more expensive. For her to travel and play at the Australian Open, it cost us about US$8,000 for an air ticket, accommodation, insurance and training."

Okutoyi's next grand slam is the French Open in May, after a series of competitions in Egypt and Italy.

And Mary has only one prayer - for the teenager to get the financial support to enable her to continue competing.

"Angella will succeed and I will celebrate," her grandmother said firmly.

Outside of tennis, Okutoyi dreams of having her own beauty and fashion business, while her future goal on court is to "play on big stages".

"I believe I can make it - playing with the big guys like Naomi Osaka and Gauff," she added.

Having created history and shown determination so far in her career, few would bet against her.