Eita Izumi is the male protagonist of the story, a high school student who moves back to his hometown after being away for four years. His family's relocation was due to his father's job, a circumstance that forced Eita to transfer schools frequently throughout his life.

In terms of appearance, Eita has wavy black hair and gray eyes, and he is typically seen wearing his traditional school uniform. His demeanor is often perceived as grumpy or emotionally reserved, which can make him seem distant or uninterested to those who do not know him well. However, beneath this seemingly impervious exterior lies a sensitive and profoundly vulnerable young man. The abrupt departure from his friends during middle school left a lasting emotional mark, and his return to the same high school, just before the end of his senior year, brings a complex mix of joy, confusion, and a deep-seated hurt that causes him to be guarded.

Eita is a diligent student. Because he spent so much time studying, due in part to his introverted nature and the disruption of constant moves, he has already secured a recommendation for admission to a university, relieving him of the pressure of entrance exams that his peers face. He was a member of the baseball club in middle school, where he worked as a pitcher for his friend and catcher, Haruto Soma. This background has left him with notable physical abilities and a particular talent for batting, which becomes a symbolic element of his character arc.

The central driver of Eita's actions throughout the story is his long-held romantic feelings for Mio Natsume, a girl he was close with in middle school. Believing his love to be unrequited, he initially tries to dismiss these emotions as a thing of the past. Despite his efforts to remain detached, he demonstrates a profound and unwavering care for the people he loves. This is most clearly seen in his relationship with Mio. He pays close attention to her struggles and, in a key moment, goes to great lengths to help her reach her university entrance exam on time during a snowstorm, showcasing a deep-seated affection and a willingness to act decisively when something is truly important to him.

Eita's role in the story is that of a quiet catalyst. His return from Fukuoka reconnects the central friend group during their final semester. He is the best friend of Haruto Soma, a relationship that endured over the years through continued messaging, with Haruto being one of the few people who knows about Eita's past feelings for Mio. Another significant relationship is with Ena Komiya, an underclassman and the president of the photography club. Ena, who initially calls him the "mysterious transfer student," becomes very persistent in wanting to use a photo she took of him for a contest. Her energetic and determined personality contrasts sharply with Eita's reserved nature, and she eventually develops romantic feelings for him, adding another layer to his interpersonal dynamics.

Throughout the series, Eita experiences notable development as he confronts his own insecurities and self-confidence issues. He struggles to reconcile his decision to not pursue Mio in the past with the resurgence of his feelings in the present. His character arc culminates in him rejecting his passive nature, symbolized by his final act of chasing after Mio to confess his feelings, a significant step for someone who had resigned himself to believing his chance had passed. His exceptional memory is a notable ability, as he can recall small details and past conversations that demonstrate how closely he has always paid attention to those he cares about, particularly Mio.