Sumi Sakurasawa, a college freshman and rental girlfriend at Chizuru Mizuhara’s agency, carries a name steeped in artistic symbolism: her surname 桜沢 blends "cherry blossom" and "marsh," while her given name 墨 ("ink") nods to traditional artistry. Her striking reddish-pink hair, braided on one side, and matching eyes shift in style to suit each rental date’s context.

Crippling shyness confines her communication to gestures, expressive glances, or typed phone messages, with speech emerging only in fragile whispers. Yet beneath her social anxiety lies quiet resolve—she joined the rental industry to confront her limitations, guided by mentor Chizuru. Through practice dates with Kazuya Kinoshita, she nurtures unspoken affection for him while honoring his bond with Chizuru.

Pre-date rituals spiral into exhaustive overthinking, once leaving her oversleeping before meeting Kazuya. A pivotal beach outing fractures this pattern: abandoning scripts, she improvises to soothe his worries about Chizuru, indirectly bolstering him through empathetic acts. Here, she breaches her silence, voicing aloud her thoughts to him—a milestone in her growth.

Her spin-off arc reveals deeper layers: idol aspirations drive her rental career as a crucible for social confidence. Observant and selfless, she aids Kazuya in supporting a grieving Chizuru, channeling acute insight into others’ emotional voids. A pet inkstone-named dog, Suzuri, mirrors her name’s ink motif, while pink hues dominate her preferences. Though her heart leans toward Kazuya, she steps back from romantic contention, carving a distinct path among her peers.