Ruka Sarashina

Ruka Sarashina is the girl with a heart condition who fell genuinely in love with a rental boyfriend — and who refuses to let that love stay transactional, regardless of how inconvenient that makes things for everyone involved.

Background

Ruka grew up with an arrhythmia that made her heart beat irregularly even in situations that should have excited her. After years of dates and relationships that failed to move her pulse, she tried the rental girlfriend service and was matched with Kazuya Kinoshita — the first person in her life to make her heart beat at a healthy rate. She interpreted this medically significant response as love, which from her perspective is entirely reasonable. She renews her rental contract repeatedly and eventually confronts Kazuya directly: she wants a real relationship, not a paid performance. She proposes a trial period, which Kazuya is too conflict-averse to cleanly refuse.

Skills

Skill	What it does
Direct Communication	Unlike most characters in the series, Ruka says what she means without significant hedging; she creates situations that force acknowledgment where others allow comfortable avoidance
Persistent Pursuit	She does not lose interest under social pressure and does not withdraw when rejected indirectly; she identifies what she wants and stays in range until the situation resolves
Emotional Honesty	Her feelings are legible to everyone around her, including Kazuya; she is not playing a long game — she is genuinely in love and does not pretend otherwise

Personality

Energetic, forthright, and operating on a different social frequency than most of the cast. Where Chizuru navigates social expectations carefully, Ruka simply says what she thinks. This makes her the most consistently honest person in Kazuya's orbit, and also the most uncomfortable — because honesty from someone you're not in love with requires confrontation rather than comfortable avoidance. She is not villainous; she is just unwilling to participate in the polite fiction that Kazuya is available.

Relationships

• Kazuya Kinoshita — the boy her heart responds to; she pursues a real relationship with him while he remains stuck on someone else, which is the series' central triangle tension
• Chizuru Ichinose — her implicit rival; Ruka knows about Kazuya's feelings and competes against them openly rather than pretending not to notice
• Mami Nanami — the ex-girlfriend whose dismissal of Kazuya set the whole situation in motion; the relationship between the two women over Kazuya is one of the series' more complicated dynamics

Role in the Story

Ruka is Rent-a-Girlfriend's complicating factor — the character who makes the central dynamic less stable by refusing to accept its unspoken terms. Her presence forces Kazuya to face questions the series would otherwise allow him to defer. She is the argument that love with good reasons and genuine depth is not automatically rewarded just because it's real.