Haruka Shinozaki is the male protagonist of the series, an ordinary second-year high school student whose life takes an unexpected turn after a confession of love. He is generally depicted as a shy and gentle boy who does not stand out dramatically from his peers, embodying the role of a typical, relatable teenager. Despite his normal exterior, he finds himself at the center of a series of increasingly awkward and comedic situations.

In terms of personality, Haruka primarily functions as the straight man among his more eccentric group of friends and acquaintances. He is often the voice of reason, attempting to navigate and correct the numerous misunderstandings that arise, particularly those stemming from his girlfriend Akiho Kosaka's misguided but sincere efforts to be a perfect partner. He possesses a vivid imagination and has a tendency to escape into sexual fantasies when under pressure, though he is generally too shy to express these desires openly. This shyness contrasts with his role as the frequent target of Akiho's blunt and misinformed proclamations about intimacy, which often result in her labeling him with embarrassing and baseless nicknames such as "Lolita, Pedo, and Masochist". While he is sometimes dense regarding the romantic feelings of other girls who are interested in him, he consistently demonstrates through his actions that Akiho is his highest priority.

Haruka's primary motivation is his relationship with Akiho Kosaka. He had been in love with her since his first year of high school, admiring her beauty and responsible nature as the class representative. After confessing on a whim and being accepted, his goal becomes navigating the chaotic and often embarrassing reality of dating her, as she pragmatically and studiously applies her research on sex to their relationship. His role in the story is therefore the catalyst for the romantic comedy; his normalcy and reactions serve as the counterpoint to Akiho's extreme behavior and the antics of the supporting cast. He is often called upon to rein in situations that have gone too far, acting as the anchor for the group's more outlandish members.

Key relationships define much of his experience. His central relationship is with Akiho Kosaka, whose earnest yet clueless approach to physical intimacy constantly leaves him flustered and acting as her guide to more conventional behavior. A significant part of their backstory reveals that when Akiho was previously isolated and the subject of gossip, Haruka was the only one who genuinely tried to understand her, a kindness that she holds dear and which forms a deep foundation for their bond. He is also surrounded by several other girls who show romantic interest in him, including his childhood friend Shizuka and his younger sister Kanata, whose cat-like clinginess leads to further misunderstandings. He even attracts the attention of a male admirer, Seiya, whose persistent but unnoticed advances add another layer of comedic confusion for Haruka, who remains oblivious.

Regarding his development, Haruka shows a consistent commitment to his girlfriend despite the constant chaos. While he does not undergo a dramatic personality transformation, he proves that his values are sound. He may have a habit of escaping into fantasy or avoiding difficult conversations, but when truly important moments arise, he prioritizes Akiho’s well-being above all else, earning the respect and affection of those around him. He learns to manage Akiho's intensity, balancing his own embarrassment with a sincere desire to make their relationship work. Beyond being just a normal guy, he has no notable special abilities or skills; his strength lies in his patience, his willingness to act as the sensible mediator, and his underlying sincerity.