Alexa Tenjouin, known as Asuka Tenjouin in the original Japanese version and as Alexis Rhodes in English localizations, is a central character in Yu-Gi-Oh! GX. She is introduced as a top student at Duel Academy, residing in the prestigious Obelisk Blue dormitory, where she is widely regarded as the queen of the female wing. Her character design, supervised by Kenichi Hara, features her in the standard female Obelisk Blue uniform, which she complements with fingerless gloves, and she has long, sporadically arranged blonde hair and brown eyes. Her name in Japanese carries the meaning tomorrows fragrance, a theme that leads to her being called tomorrow girl by another character.

Alexis is defined by a personality that contrasts sharply with many of her elitist peers. She is confident, strong-willed, brave, and kind, possessing a natural humility that prevents her from looking down on students from lower-ranked dorms like Slifer Red. Despite being one of the most beautiful and skilled female duelists at the academy, she never intentionally uses her appearance to her advantage and is often embarrassed by the arrogant behavior of her fellow Obelisk Blue students. While many male characters develop crushes on her, including Chazz Princeton, she consistently states she is not looking for a boyfriend and dedicates herself to her goals. Over the course of the series, however, she develops deep, though often unspoken, feelings for Jaden Yuki, a friendship that becomes one of her most important relationships. She is also deeply loyal to her older brother, Atticus Rhodes, whose mysterious disappearance before the start of the series is her primary motivation in the early story. She works closely with Zane Truesdale, her brothers best friend, to search for clues about what happened to him.

Her role in the story evolves significantly across the seasons. In the first year, she is a key ally in the battle against the Shadow Riders, the seven duelists sent to unleash the Sacred Beasts. Her personal stake becomes clear when it is revealed that the Shadow Rider known as Nightshroud is actually her brainwashed brother. After Jaden defeats Nightshroud, Alexis duels another Shadow Rider, Titan, to restore Atticuss lost memories, succeeding in her mission. In the second year, she faces a major challenge when Chazz, now a member of the Society of Light, attempts to take over the Obelisk Blue dorm. She duels him to stop him but loses, and as a result, her mind is also brainwashed by the societys leader, Sartorius. She is made an Apostle of Light, becoming cold, arrogant, and cruel, even to her best friends, Jasmine and Mindy. She is eventually freed after being defeated by Jaden. In the third year, she follows Jaden into a parallel dimension to rescue a friend, only to be captured and seemingly sacrificed by the King of the Dark World to activate a powerful card. While she is ultimately saved and returned to Duel Academy, this traumatic event contributes to a growing distance between her and Jaden. In the final year, she struggles with Jadens darker and more serious personality and her own uncertain future. She becomes frustrated with what she sees as his neglect but eventually reconciles with him during a tag duel tournament. After these events, she makes the decision to leave Duel Academy to study abroad, a choice heavily influenced by Jaden. During their farewell conversation, she displays strong romantic feelings for him but does not outright confess, instead expressing her gratitude for having met him. Her final storyline sees her confronting her deepest fear, which is failing as a teacher, during an invasion by creatures of darkness, but she is inspired to overcome it by remembering Jaden.

As a duelist, Alexis is one of the academys elite, known for her strategic and balanced tactics. Her primary deck theme revolves around Cyber Girl monsters, which include Warrior and Fairy-type monsters based on dancers, gymnasts, and skaters, such as Etoile Cyber, Blade Skater, and Cyber Tutu. She is skilled in Fusion Summoning, with her key fusion monster being Cyber Blader, whose powerful effects change based on the number of monsters her opponent controls. Later in the series, she also adopts a series of powerful Ritual Monsters known as the Cyber Angels, including Benten, Idaten, and Dakini. During her time brainwashed by the Society of Light, she uses a different deck based on ice and the White Night theme, which focuses on immobilizing the opponents monsters and negating spell and trap cards. Her abilities and resilience make her a formidable opponent and a key member of the main cast.