Alexandra Garcia, often called Alex by those close to her, is a former professional basketball player from the United States who serves as a crucial mentor to two of the series' key characters. Standing at 180 centimeters tall and 31 years old during the events of the story, she has long blonde hair and typically wears glasses. Her background as a champion in the American college league and a former player in the WNBA gives her a level of experience and knowledge that few others in the series possess. Her career was unfortunately cut short due to an eye disease that impaired her vision, forcing her into an early retirement.

Following her retirement, Alexandra struggled to find purpose and turned to playing basketball for money on street betting courts. It was during this difficult period that she was approached by two young boys, Taiga Kagami and Tatsuya Himuro, who asked her to teach them basketball. Initially annoyed by them, her feelings gradually changed as she witnessed their growing passion for the game, and she eventually found happiness and a renewed sense of purpose in teaching them and other local children. This experience allowed her to regain her composure and establish herself as a coach at a local basketball club.

Alexandra possesses a bold and uninhibited personality that often stands in stark contrast to the more reserved characters in Japan. She is very flirty and physically affectionate, freely kissing those she likes, including her former students Kagami and Himuro, as well as Riko Aida from Seirin High. She is also known for her carefree attitude towards clothing, sometimes appearing in her apartment wearing only a t-shirt and underwear, much to the embarrassment of others. Despite this flamboyant exterior, she is also highly clever, observant, and an excellent judge of basketball talent and potential. She has shown she can be serious and intimidating when the situation calls for it, even demonstrating some fighting expertise.

Her primary role in the story is as a mentor and source of advanced training for Kagami, especially in preparation for the Winter Cup. She travels to Japan specifically to watch the matches between Kagami and Himuro, her two prized pupils. During her stay, she takes charge of Kagami's special training regimen. One of her most notable contributions is forcing Kagami to play high-stakes streetball games to teach him the animal instinct, a survival-of-the-fittest mentality needed to sharpen his reflexes. She also analyzes opposing players with great accuracy, such as identifying the threat of Yosen High's players and being impressed by Shintaro Midorima's skills.

Her key relationships are with Kagami and Himuro, whom she views with deep affection. She has stated that she might consider a romantic relationship with them if they were older. For her, their rivalry is both a source of pride and personal difficulty, as she is emotionally invested in both of them. She also forms a bond with the members of Seirin High, becoming an informal consultant and support system for the team during the tournament.

Alexandra's personal development is a quiet but important part of her character. Having lost her professional career due to illness, she found a new purpose and joy in life by passing on her knowledge to the next generation. Watching Kagami and Himuro grow and eventually face each other allows her to see the fruition of her work as a mentor, giving her a sense of fulfillment that replaces the void left by her retirement. She is bilingual, fluent in both English and Japanese, and her hobbies include watching anime and barbecuing. Her most significant technical contribution to the series is teaching Kagami the Meteor Jam, a powerful dunk that becomes one of his signature moves.