Riko is a human girl appearing in the "Vampire Shahal" OVA of the Owari no Seraph series. She possesses short brown hair and brown eyes. Her striking resemblance to Lana, Shahal's younger sister, resulted in her kidnapping by the vampire Shahal. Riko wears a long-sleeved dark pink dress featuring ribbons tied at the arms, a large black ribbon at her throat, white ruffled hems, and additional black ribbons at her waist and back, paired with simple dark pink slippers. Riko exhibits a caring and sympathetic personality. Despite her abduction, she expresses sorrow for Shahal upon learning he was once human, explaining to Yuichiro Hyakuya that she feels pity for his circumstances. Her known story begins when Guren Ichinose assigns the Shinoa Squad a mission to rescue her from Shahal and return her to her family. During captivity, Shahal mistakes her for his sister Lana, becoming protective while refusing to acknowledge her fear of his vampiric appearance. When Riko points out she is not Lana and voices concern about his fangs, Shahal deflects by offering her a hair accessory. Riko eventually sympathizes with him, attempting to shield him from a vampire ambush. Ferid Bathory intervenes during this ambush, snatching Riko and drinking her blood to provoke Shahal. Ferid mocks Shahal by calling Riko a "doll" and ridiculing his attempts to recreate a familial bond. Guren Ichinose initiated the rescue operation by deploying the Shinoa Squad. Riko's key relationships are with her captor Shahal, her antagonist Ferid Bathory, and her rescuer Guren Ichinose.