Kazuya Kinoshita, a college student grappling with low self-esteem and indecision after his breakup with Mami Nanami, impulsively rents girlfriend Chizuru Mizuhara through the Diamond app. To shield his family—particularly his doting grandmother Nagomi—from disappointment, he fabricates a romance with Chizuru, sparking a web of deception that intensifies as they discover they are neighbors and classmates.

His compulsive lying stems from a fear of confrontation and an earnest desire to shield others’ emotions, yet beneath this flaw lies a core of selflessness. He spearheads a crowdfunding initiative to finance a film advancing Chizuru’s acting career, showcasing sharp analytical skills in budgeting and project management. In moments of crisis, such as rescuing Chizuru from a capsized boat, his latent courage surfaces.

Kazuya’s arc traces a transformation from social awkwardness to self-aware determination. Steadfast loyalty to Chizuru anchors him amid advances from Ruka Sarashina’s relentless pursuit and Sumi Sakurasawa’s timid affection. He rebuffs Ruka’s overtures to honor Chizuru, while gently guiding Sumi through her social anxiety, reflecting his empathetic depth.

Raised in a family-run liquor store and studying business administration, Kazuya shares a deep bond with his grandmother, whose approval fuels his charade. His passion for marine biology emerges during aquarium visits, where he imparts aquatic trivia. Though initially prone to impulsive decisions and risqué thoughts, he cultivates restraint, confronting his dishonesty and impulsiveness.

Kazuya’s resilience shines as he navigates comedic blunders and heartfelt growth, driven by relationships that challenge his insecurities. From ensuring Chizuru’s film succeeds to balancing romantic entanglements, his journey underscores perseverance, self-improvement, and the redefinition of love. His blood type, A, occasionally nods to cultural symbolism shared with Chizuru, subtly threading through their dynamic.