Kazuya Mizuno, a childhood friend of Nodoka, transitions their bond into romance during high school, initiating a partnership still in its nascent, developing phase. He habitually teases Nodoka, creating a dynamic that appears lighthearted and casually unserious to outsiders. Despite this demeanor, he demonstrates unwavering commitment through a promise to remain with her indefinitely.

Their relationship’s stability fractures when Ozaki blackmails Nodoka into a physical affair. This coerced secret breeds emotional and physical distance between Nodoka and Kazuya, igniting significant conflict. Unaware of Nodoka’s betrayal or the blackmail’s grip, Kazuya remains ignorant of the coercion corroding their bond. His obliviousness starkly contrasts Ozaki’s manipulations, which exploit the fledgling, non-intimate nature of Kazuya and Nodoka’s relationship.