Hajime Ichijou is Nonoka Aida's childhood friend who reappears in her life after returning from Poland with his father. His arrival is prompted by a pact between their fathers, fulfilling Nonoka's father's deathbed wish for their marriage. This pact fuels Hajime's persistent pursuit of Nonoka despite her initial reluctance and young age.

He exhibits a confident, assertive, and possessive personality toward Nonoka. Hajime openly challenges her other suitors, Yuya Hashiba and Shinobu Oda, positioning himself as a direct competitor for her affections. His approach is bold, including moments of physical forwardness such as an attempted non-consensual advance at the end of the first OVA episode which he halts himself before escalation.

A skilled judo practitioner, Hajime surpasses Yuya in their initial confrontations. His physical prowess features prominently during a formal engagement ceremony where Yuya challenges him to a judo match for Nonoka's future. Hajime dominates the match initially but loses when Shinobu intervenes by revealing a vulnerable point to Yuya, enabling Yuya's victory.

Following his defeat, Hajime returns to Poland but vows to continue pursuing Nonoka. He later reappears unexpectedly at her school, replacing Shinobu at the piano, signaling his unresolved intentions and persistent presence.

His relationship with his father reinforces his determination, as both uphold the marriage pact as binding. This dynamic contributes to the pressure on Nonoka, framing Hajime's actions within a familial obligation regardless of her feelings.