Hayato Oda is a first-year university student who attends the same seminar as Ai Sunakawa, the older sister of Takeo Goda's best friend, Makoto Sunakawa. He is a young man of medium height with wavy brown hair and hazel eyes, and he wears a single earring in his left ear, which gives him a slightly rakish appearance. On the surface, Oda comes across as a handsome, carefree, and somewhat irresponsible individual. His friends often perceive him as frivolous and a bit of a playboy, and his easygoing manner can sometimes be mistaken for smugness or pushiness. However, this exterior hides a far more sincere and devoted personality. He is naturally cheerful, bright, and exceptionally sociable, possessing a core of loyalty and determination that becomes evident when he is faced with a challenge.

Oda's primary motivation and most significant storyline stem from his deep affection for Ai Sunakawa. His feelings for her were sparked by a specific incident: after carelessly losing important documents entrusted to him by a professor and finding himself in a difficult situation, Ai was the one who scolded and encouraged him, helping him to overcome the problem. This act of tough love transformed his casual interest into a powerful and genuine love. Upon discovering that Ai harbored a long-standing secret crush on Takeo Goda, Oda did not retreat. Instead, his determination solidified, leading him to travel from Nagoya to Tokyo to see for himself the kind of man who had captured Ai's heart. His initial plan was to help Ai resolve her lingering feelings for Takeo, even if it meant meddling in her personal affairs. He orchestrated a group outing to an amusement park with the intention of creating a situation where Ai could confess her feelings to Takeo, believing this was the only way she could truly move on. While his methods are undeniably overbearing and self-serving at first, he possesses a fair amount of self-awareness and acknowledges his own flaws and weaknesses along the way.

Within the story, Oda serves as a catalyst for Ai's emotional growth, pushing her to confront her unrequited feelings for Takeo so that she might find happiness elsewhere. His role brings a different kind of romantic dynamic to the series, showcasing a more assertive and proactive pursuit of love. His key relationship is, of course, with Ai Sunakawa. He persists in courting her with a unique blend of tenacity and respect, never becoming pushy in a disrespectful way. An interesting quirk of their dynamic is that he always uses very polite and formal language when speaking to her. This habit began because he initially believed Ai was older than him, and even after discovering they are the same age, he has been unable to drop the formality, which adds a layer of endearing awkwardness to his advances. His interactions with Takeo are initially those of a rival, but he quickly learns that Takeo is completely devoted to his girlfriend, Yamato, and poses no threat to his chances with Ai.

Oda’s development throughout his appearance in the series is significant. He evolves from a somewhat meddlesome outsider into a more selfless figure who genuinely wants Ai to be happy, even if that happiness seems elusive. After hearing Ai's true feelings and realizing the strength of her love for Takeo, he returns to Nagoya and continues to actively and sincerely pursue her, not with the goal of forcing her to forget Takeo, but in the hope that she might one day come to see him as a new possibility for her future. He does not possess any supernatural or extraordinary abilities, but his notable skills lie in his social intelligence and emotional resilience. He is adept at navigating complex social situations, perceptive enough to understand the feelings of those around him, and refuses to give up on his goals despite repeated rejections, showcasing a level of emotional maturity that makes him a genuinely compelling character.