At 33, Jahleel Weaver has pretty much won the celebrity-stylist lottery.

As deputy creative director of Fenty, the women’s ready-to-wear and accessories line introduced by Rihanna in May, his days are spent working alongside a nine-time Grammy Award winner whose clothing brand is backed by LVMH, the French luxury conglomerate, and released to her passionate fans without regard to conventional seasonal rhythms.

Theirs is a close relationship. “We talk almost every day,” Mr. Weaver said. “I feel I’m her little brother.” Though Rihanna is younger, at 31.

“Creatively, he is my right hand,” she wrote of Mr. Weaver in an email, “but at the same time, it’s as if we’re family.”

The path that led Mr. Weaver to help guide the most talked-about fashion debut of 2019, founded by one of the most influential women in popular culture, was a long and gently winding one.

At 18, he moved from suburban Maryland to New York to study fashion design at LIM College. Mr. Weaver helped support himself by working in sales at Jeffrey, the high-end retailer in the meatpacking district known for its extensive shoe department and attentive customer service.

He quickly met some famous clients, many downtowners working in music, and began to style several. “To be working for, and building a brand,” Mr. Weaver said, “I always think about my experience at Jeffrey.”

Mr. Weaver was also making inroads working as a freelance stylist away from the store, and it was on one of these gigs that he met Mel Ottenberg, who is currently the creative director of Interview magazine. Mr. Ottenberg had just begun collaborating with Rihanna on her 2011 “Loud” tour and brought Mr. Weaver on to assist him.

Soon enough, Mr. Weaver and Rihanna became inseparable, traveling the globe together. (Mr. Ottenberg continues to style Rihanna on occasion, as he did in 2018, dressing her when she was a host of the Met Gala in a dazzling jewel-embroidered, papal-inspired Margiela ensemble.)

When Rihanna decided in 2014 to start the umbrella company Fenty Corp., giving it her last name, she asked Mr. Weaver to join as a junior creative director.

He was there to help her create the beauty line, Fenty Beauty, which soon had legacy cosmetics brands scurrying to broaden the colors of foundation on offer; and Savage x Fenty, a line of inclusive, body-positive-inspired lingerie, the show of which had fashion week attendees squealing in September; and Cameo, her everything-old-is-new-again jewelry line.

“The most valuable thing Jahleel brings to the process,” Rihanna said, “is his complete understanding of my vision.”

Virgil Abloh, the founder of the cult street-wear-inspired fashion line Off-White and the artistic director for men’s wear at Louis Vuitton (also part of LVMH), said that the creative dynamic between Rihanna and Mr. Weaver has resulted in “looks that are cemented within popular culture.” (Fuzzy slides were just the beginning.)

Mr. Abloh first came to know Mr. Weaver through what he refers to as an “international tribe of creatives,” a community of designers and artists constantly on the move.

Mr. Weaver, though he continues to travel extensively, now lives primarily in Paris. He moved there in early 2018 to begin work on Fenty’s debut, a fairly stressful undertaking.

“How do you put everything that Rihanna represents into one collection?” Mr. Weaver said.

The answer came to the pair late one night in the form of a music metaphor: an album and its release. Rather than settle on distinct, themed collections shown twice a year, Fenty would drop capsule collections throughout the year, much as singles are released over the course of an album’s rollout.

This would heighten anticipation and set the brand apart from the grind of the fashion pack.

“Each release,” Mr. Weaver said, “can speak to something different,” with inspiration taken from various aspects of Rihanna’s personal style, be it sleek futurism or the history of Cameo.

“At the end, you have a full album, a full body of work,” Mr. Weaver said. “I think that’s the beauty about our release schedule — there’s a piece of Fenty for everything you might need to get dressed.”

Basing Fenty’s strategy around online drops was a radical move, jolting the old seasonal schedule with the hectic cadence of fast fashion. But Fenty has been even more cutting-edge in giving people of color a place at the top of an industry still plagued by racial inequality and insensitivity.

When Bernard Arnault, the chairman of LVMH announced Fenty, Rihanna became the first woman and person of color to establish a house with the luxury retail giant. At a time when high-profile brands continue to be plagued by racist missteps — just this year Gucci was forced to recall a balaclava knit-top that resembled blackface — the significance of Fenty’s debut was not lost on Mr. Weaver.

“All the barriers that were broken in that one day, with that one announcement,” he said. “I actually cried.”

Along with Mr. Abloh at Louis Vuitton and Olivier Rousteing running Balmain, Rihanna’s entry into the field was further evidence to many that change, however overdue, is finally coming to the upper echelons of luxury fashion.

Mr. Weaver is feeling optimistic. “Because of people like Ri constantly breaking barriers,” he said, “it makes it a lot easier to exist in space where representation for people of color didn’t necessarily exist.”

And his own place in that space?

“Honestly,” Mr. Weaver said, “I think I’m still pinching myself.”