Tatsuya "Tacchan" Uesugi, elder twin to Kazuya Uesugi, struggles with indecision and a self-effacing nature, habitually sidelining his own desires to accommodate others. Clinging to unresolved feelings for childhood friend Minami Asakura—a sentiment mirrored yet unspoken by Kazuya—he buries his emotions, outwardly championing his brother’s bond with Minami while privately navigating quiet heartbreak. Avoiding baseball, a cornerstone of Kazuya’s identity as Meisei High’s star pitcher, he retreats to the boxing club, lingering on the margins of his twin’s athletic pursuits as a detached spectator.

A defining crisis ignites his metamorphosis, forcing him to grapple with long-suppressed yearnings and obligations. Spurred by a need to honor Minami’s hopes and untangle his inner turmoil, he abandons boxing for baseball, signaling his slow ascent from Kazuya’s shadow. This choice sparks the awakening of his athletic prowess and emotional fortitude, as he treads the precarious line between self-denial and self-discovery, torn between bolstering his brother and forging his own path.

Through layered arcs, his altruism persists as a core trait, maturing into deliberate, purposeful devotion. Harnessing his latent baseball talent into measurable progress, he commits to actualizing Minami’s aspirations and mending fractured familial ties. His evolution from bystander to architect of his destiny mirrors a complex dance of brotherly loyalty, quiet rivalry, and the pursuit of individuality.