Rina is a woman who appears in Rena's life in the story Tsumihoroboshi-hen. She is the lover of Teppei Houjou, and together they swindle men out of their money through intimidation and blackmail schemes.
Her real name is Ritsuko, but she uses Rina as a fake name. Rena kills her to protect her father. She is killed in Tatarigoroshi-hen, when her body was found in a bag in a stormdrain after having been tortured to death by an unknown assailant, in Minagoroshi-hen, when she is murdered by members of the yakuza when she tries to flee Okinomiya, and in Miotsukushi-hen, where she is killed by Takano. Her death often triggers Teppei's return to Hinamizawa.