Akira Tsubaki is the main protagonist of the story and a seventeen-year-old second-year student in Class 2-A at the municipal Kazamidai High School. In many respects, he is depicted as an extraordinarily ordinary young man, with his best friend describing him as someone whose athletic abilities and academic grades are perfectly average, but who is a fundamentally good person at heart. He is officially a member of the film research club, though he attends meetings so infrequently, perhaps only two or three times a year, that he is considered a ghost member.

Tsubaki’s life takes an unexpected turn when he becomes intrigued by a new transfer student, Mikoto Urabe. One day after school, he wakes her from a nap at her desk, and after she leaves, he spontaneously tastes a puddle of drool she left behind on the surface. This inexplicable act triggers a severe, illness-like condition that Urabe later identifies as lovesickness, specifically a form of withdrawal caused by the absence of her saliva. This bizarre incident forms the foundation of their secret romantic relationship, though Urabe is clearly the one who holds the dominant position within it.

As a character, Tsubaki is portrayed as a mellow and relatable teenage boy. He is neither an overly perverted caricature nor a boy who recoils in fear from female attention, reacting to the strange situations he finds himself in with a sense of understandable bewilderment and acceptance. He is genuinely curious about girls and romance, often comparing his own slow-moving relationship to those of his classmates and feeling that there is a lack of typical romantic progress between him and Urabe. Despite his curiosity, he is not very aggressive in pushing for physical intimacy, a hesitation partly fueled by a healthy fear of Urabe’s more unpredictable and dangerous habits, such as her expert skill with a pair of scissors she keeps hidden in her panties.

His motivations are largely driven by the unique mechanics of his bond with Urabe. To prevent the recurrence of the painful withdrawal symptoms, he must ingest a sample of her saliva every day, a ritual they perform when walking home from school. This exchange of drool serves as the core of their communication and intimacy, as it allows him to directly sense her feelings and emotions. Over time, his initial bewilderment deepens into a genuine effort to understand Urabe and navigate the complexities of their unusual relationship, as he seeks to make it feel more like what he perceives a normal relationship to be.

Tsubaki’s home life provides essential context for his personality. His mother passed away when he was very young, leaving him with almost no memories of her. Consequently, he was raised by his sister, who is seven years older than him and took on a maternal role in the household. This background adds a layer of emotional depth, as the story later reveals through the mysterious properties of Urabe’s saliva that he did experience profound grief as a child, even if he cannot consciously recall it.

In terms of his role in the story, Tsubaki acts as the audience’s surrogate, the normal boy navigating the extraordinary mystery of his girlfriend. His perspective guides the narrative, and his personal development is measured by his growing acceptance and understanding of Urabe’s mysterious nature. A few other notable traits include his skill at bowling, which he claims is his only redeeming quality, and his fandom of a pop idol named Momoka Imai, who bears a strong resemblance to Urabe.