Rina Mamiya

Rina Mamiya — whose real given name is Ritsuko Mamiya — first appears in Tatarigoroshi-hen and later serves as the antagonist of Tsumihoroboshi-hen and Miotsukushi-hen. On paper she is the private manager of the Sonozaki-run hostess club Blue Mermaid, but in practice she works the floor herself, drawing money and gifts from her clients. Her lover and self-appointed pimp is Houjou Teppei; together the two run loan-sharking, blackmail, and various intimidation scams against the men she meets through the club.

In most versions of the story, Rina dies off-screen: former yakuza associates catch her trying to steal from the Sonozaki-linked organization and execute her in a manner echoing old Watanagashi-era rites, leaving her mutilated body to be found in a storm drain. Teppei had no part in the theft, but news of her death still panics him into fleeing back to Hinamizawa, where he moves in on and abuses Houjou Satoko. In Tsumihoroboshi-hen, Rina instead survives longer, seducing Ryuuguu Rena's father to extort him for money. When Rena uncovers the scheme and confronts her at the dump, Rina turns violent, and Rena kills her in self-defense — an act that reawakens Rena's Hinamizawa syndrome.

Behind a warm, sympathetic manner lies a calculating manipulator who is sharper and more cautious than Teppei, though reckless enough to gamble on robbing the yakuza outright. Later material, including Oniakashi-hen and its manga adaptation, shows a softer side of Rina: she genuinely feels guilty for exploiting Rena's father and sees a kindred spirit in Rena, another child raised by a single parent as she herself once was. She eventually tries to end the relationship on her own initiative, though this rarely saves her.

Rina is recognizable by her bubblegum-pink hair, gold tube top, and a distinctive perfume that Rena finds unpleasant, along with a star-shaped tattoo on her midriff.