Miyuki Hoshizora, a 14-year-old transfer student to Nanairogaoka Middle School, radiates bright optimism and energetic joy, frequently expressing her exuberance with the catchphrase "Ultra Happy!" Her deep affection for fairy tales fuels her cheerful outlook. This enthusiasm often manifests as clumsiness, leading to frequent accidents like tripping or being struck by objects. Despite her generally cheerful demeanor, unfamiliar situations such as class introductions or stage performances can trigger nervousness and moments of naivete. Her current outgoing nature stems from a significant childhood transformation. Originally timid and reserved, Miyuki struggled to interact with others until her grandmother, Tae, gifted her a mirror necklace and encouraged her to practice smiling. An encounter with an unidentified girl further catalyzed her shift towards her present personality. This history underpins her strong aversion to seeing others sad or crying, driving her motivation to spread happiness. As leader of the Smile Pretty Cure team, Miyuki transforms into Cure Happy, wielding holy light-based powers including high jumping and her signature "Happy Shower" attack. Her Cure form features bright pink hair lengthened into braided pigtails, a tiara, feather accessories, and a pink dress with a magenta bow. Advanced transformations—Princess Happy, Tiara Mode, and Ultra Cure Happy—enhance her appearance with longer, wavier hair, elaborate crowns, angelic wings, and rainbow-accented garments, appearing in both series and film contexts. During the events of *Precure All Stars New Stage: Mirai no Tomodachi*, Miyuki travels to Yokohama with her team to find fragments of the villain Fusion. She accidentally bumps into Ayumi Sakagami, a lonely girl who befriended a Fusion fragment named Fu-chan. When Fu-chan grows hostile and absorbs the Cures' attacks, Miyuki demonstrates empathy for Ayumi's isolation. After Fu-chan consumes Ayumi's mother and attacks the city, Miyuki reassures Ayumi they can rectify the situation. In the final battle atop a tower, Miyuki shields Ayumi from Fusion's assault. Following Fu-chan's sacrifice empowering the Smile team's victory, Miyuki witnesses Ayumi's newfound confidence. In *Precure All Stars New Stage 2: Kokoro no Tomodachi*, Miyuki attends a fairy school party where the villain Kage crystallizes her and her teammates after stealing their transformation devices. While partially crystallized, she communicates forgiveness to Enen, a fairy who assisted Kage, and instructs him to seek help from the Doki Doki Pretty Cure team. Her encouragement inspires Enen to relay her message. Rescued by her team, she later partners with Cure Heart to combat Kage, showcasing camaraderie with newer Cures. Beyond the *New Stage* films, Miyuki appears in franchise anniversary celebrations for *HappinessCharge PreCure!* and *Hirogaru Sky! Pretty Cure*. A light novel continuation set 10 years after the series depicts her working in a bookstore and bonding with a girl named Yoshimi, maintaining her affinity for stories and supporting others. Her relationships emphasize emotional support. She admires teammates like Akane (Cure Sunny) for athleticism and Nao (Cure March) for bravery, actively encouraging them during low moments. She shares notable similarities with Yayoi (Cure Peace), including parallel reactions to exciting events.