Rikka Hishikawa is one of the main characters in the anime series 'Dokidoki! Precure.' She is a highly intelligent and responsible girl, known for her calm demeanor and caring personality. Rikka is a close friend of the protagonist, Mana Aida, and serves as her confidante and advisor. As Cure Diamond, her Precure alter ego, she uses her wisdom and strategic thinking to help the team overcome challenges and protect the world from evil forces.