Natsu Takasaki is the female protagonist of Baby Steps and a central figure in the story. She attends the same high school as the main character, Eiichiro Maruo, and is a member of the Southern Tennis Club (STC). From a young age, Natsu has played tennis and is determined to become a professional player. Her background includes a supportive family and a childhood friendship with Souji Ike, a world-class tennis prodigy who later becomes a benchmark for her own ambitions. On the court, Natsu is a highly skilled all-round player and consistently ranks among the top seeds in female junior tournaments in Japan. Her playing style contrasts sharply with Eiichiro's analytical approach: she relies on instinct and intuition, reacting to the flow of a match and her opponent's demeanor rather than on data or pre-planned strategies. She possesses a natural, sustained concentration that allows her to maintain focus throughout a match, though she occasionally struggles with nerves in early-round matches of major tournaments.

Personality-wise, Natsu is bright, cheerful, and outgoing, often described as one of the most popular girls in her school year. She is friendly and approachable, but beneath her easygoing exterior lies a fierce competitive drive and a deep passion for tennis. She does not dwell on details or overthink situations, preferring to act on her feelings, yet she is also capable of serious dedication when it comes to training and self-improvement. Her primary motivation is to reach the professional level and compete on the world stage, a goal that she pursues with unwavering commitment. At the same time, she becomes a key source of inspiration for Eiichiro, encouraging him to take tennis seriously from their first meeting and supporting his growth as a player.

Natsu’s role in the story is multifaceted. She serves as the primary love interest for Eiichiro, and their relationship develops gradually from mutual respect and admiration to a romantic partnership that endures through long-distance challenges—she chooses to attend college in America while continuing her tennis career, and they maintain a long-distance relationship. She also acts as a constant benchmark for Eiichiro’s progress, as her own skill level represents a high standard that he strives to approach. Beyond their romantic connection, Natsu has key relationships with other characters. She shares a close friendship and healthy rivalry with Aki Shimizu, another top female player at STC, whose more disciplined, analytical style contrasts with Natsu’s instinctive approach. Takuma Egawa, a powerful male player at STC, harbors complicated feelings for her at first but eventually respects her relationship with Eiichiro. Her childhood friend Souji Ike remains a distant but influential figure, representing the world-class level she aims for.

Over the course of the series, Natsu undergoes significant development. She learns to manage her early-match nerves and refine her instinctive play into a more consistent weapon. Her biggest breakthrough comes when she wins the All-Japan Junior Tennis Tournament, defeating her rival Aki Shimizu in the final. This victory solidifies her status as the top junior female player in Japan and brings her closer to her professional goal. Simultaneously, her personal growth is intertwined with her relationship with Eiichiro: she becomes more open about her feelings and learns to balance her competitive ambitions with emotional connections. In terms of notable abilities, Natsu’s instinctive tennis makes her unpredictable and dangerous, especially when she enters a state of flow. She reads opponents’ intentions through body language and atmosphere, and her all-round skill set allows her to adapt to various playing styles. Her physical conditioning and athleticism are strong, and she possesses a natural resilience that helps her recover from setbacks. Overall, Natsu Takasaki is a talented, determined, and emotionally grounded character whose journey mirrors the series’ theme of taking steady, incremental steps toward greatness.