Kana Orikura lives with her mother and younger sister Manami. When Yoshihiko Mizusawa's father transferred, Kana's family hosted him in their home; she greeted his arrival with hostility. As a high school senior facing graduation and college entrance exams, Kana confessed romantic feelings to her upperclassman Yoshihiko moments before he departed for college. They shared their first kiss and began a relationship. After Yoshihiko's move, their long-distance relationship strained under his demanding college schedule and infrequent communication. Kana felt profound loneliness, neglect, and depression, causing her academic focus to deteriorate as she fixated on doubts about Yoshihiko's loyalty.

Her emotional state grew more complex with the arrival of Shogo Hayakawa, a young temporary teacher assigned to her class. Kana was immediately struck by Shogo's strong physical resemblance to her deceased father. The situation intensified when Shogo, revealed as a distant relative and cousin of her late father, moved into the Orikura household, occupying Yoshihiko's former room. This proximity sparked confusion within Kana, leading her to question if her love for Yoshihiko stemmed from genuine emotion or merely the convenience of their past daily closeness.

Despite developing a noticeable attraction to Shogo, Kana maintained her devotion to Yoshihiko. Their relationship reached a critical juncture during Yoshihiko's rare visit, where he expressed visible concern and discomfort over her closeness to Shogo. This confrontation forced Kana to face the realities of her long-distance relationship and her own wavering feelings, serving as a catalyst to evaluate the depth and sustainability of her commitment to Yoshihiko amidst these new emotional challenges. Throughout this period, her supportive mother offered gentle encouragement.