Itsuki Myōdōin, a 14-year-old student council president at Myōdō Academy Junior High School and granddaughter of the academy's president, initially presents herself masculinely. She wears boys' uniforms and adopts boyish mannerisms to assume the role of heir to her family's martial arts dojo, a responsibility her chronically ill older brother Satsuki cannot fulfill. Despite this outward presentation, she privately enjoys traditionally feminine interests like cute dolls and fashion, interests she suppresses to maintain her chosen image. Her internal conflict between this self-imposed masculine role and her feminine interests defines her development. After Cure Blossom purifies her stolen Heart Flower—a peony symbolizing rebirth and noble spirit—she gradually embraces her femininity. This includes designing a dress, joining the school's fashion club encouraged by Hanasaki Tsubomi and Kurumi Erika, and accepting that her martial arts dedication can coexist with her feminine interests. A pivotal moment comes when Satsuki affirms her dress looks cute, helping her reconcile these aspects. She transforms into Cure Sunshine, the Heartcatch Pretty Cure team's third Cure, motivated by her desire to protect Satsuki. This transformation occurs when she shields the fairy Potpourri from the Desert Messenger Sasorina, declaring her resolve to become someone who protects others. This act activates the Shiny Perfume, enabling her transformation. She names herself Cure Sunshine upon seeing sunlight during the battle, referencing her brother's past encouragement and the "light" kanji in her family name. Her theme flower is the sunflower. Cure Sunshine's abilities include the "Gold Forte Burst" attack. She later achieves an upgraded form, Super Cure Sunshine, after passing the "Trial of the Super Silhouette" at the Pretty Cure Palace. This trial forces her to confront a past version accusing her of abandoning martial arts and her brother. She overcomes this self-doubt by declaring she incorporates her love for fashion and cute items to make Satsuki smile, without abandoning her core commitments. This acceptance unlocks the Super Silhouette power. As threats intensify, she prioritizes her Pretty Cure duties, deciding against re-election as student council president to focus on protecting others. During antagonist Dune's return, she fights alongside her team but is defeated. Awakening in a desertified world, she immediately searches for her family, demonstrating her protective instincts. She expresses visible relief upon reuniting with Satsuki, saved alongside others protected by the Pretty Cures. In *Precure All Stars New Stage: Mirai no Tomodachi*, Cure Sunshine appears with the combined Pretty Cure teams battling villain Fusion's remnants in Yokohama. Her fairy partner Potpourri helps protect the human girl Ayumi Sakagami. Cure Sunshine fights alongside the Heartcatch team and other Cure groups, including Fresh Pretty Cure, holding back Fusion's spawn and supporting the Smile and Suite Pretty Cure teams during the climactic battle, providing defensive support and teamwork consistent with her character. Her personality combines calmness, kindness, and a principled, protective nature. She maintains a formal, princely demeanor, willing to defend others but capable of sternness when necessary. Her relationship with Potpourri centers on their shared protective desire despite initial inadequacy. Bonds with Tsubomi and Erika deepen through their encouragement of her self-acceptance, while her relationship with Tsukikage Yuri evolves from initial distance to mutual trust and teamwork.