Tsubomi Hanasaki, a timid 14-year-old second-year at Myoudou Academy, moves to Kibougahana City with her family to run the Hanasaki Flower Shop. Her name, signifying "blooming flower bud," mirrors her floral connection, rooted in her birth under a budding tree. Shy and introverted, she wears round glasses that fog when nervous and struggles socially, shaped by childhood loneliness during her parents' frequent business trips while under her grandmother Hanasaki Kaoruko's care. Witnessing birds care for their young once moved her to tears over her isolation, prompting her parents to prioritize family by opening the flower shop.

Kind, bookish, and deeply passionate about botany, Tsubomi dreams of becoming a botanist to "make flowers bloom in desolate spaces," even other planets, driving her later English studies. Though planning to join the Gardening Club at school, the energetic Erika Kurumi persuades her into the Fashion Club, initiating her self-reinvention. She speaks with old-fashioned patterns influenced by her grandmother and harbors a romanticized view of love, often reacting dramatically to romantic situations.

Her transformation into Cure Blossom occurs when the Desert Apostles steal Erika's Heart Flower. Overcoming fear and reluctance, Tsubomi accepts the role to save her friend, becoming the pink-themed Cure Blossom, symbolizing cherry blossoms. Her battle cry, "I can't stand it anymore!" or "My bag of tolerance has snapped!" signals her resolve. As Cure Blossom, her maroon hair brightens to pink, lengthens into a ponytail with flower accessories, and she dons a white mini-dress featuring petal motifs and a cherry blossom brooch. Initially clumsy in combat, dubbed the "Weakest Pretty Cure in History," she develops attacks like Blossom Screw Punch, Blossom Flower Storm, and her finishing move, Pink Forte Wave, using the Blossom Tact to purify enemies. Later power-ups include Super Silhouette (with pearl-pink details and a tiara) and Rainbow forms (featuring feather-like embellishments and neon hair).

Tsubomi's character development focuses on overcoming shyness through friendships. Erika's extroversion challenges and ultimately strengthens her, fostering assertiveness. She admires student council president Itsuki Myoudouin, initially mistaking her for a boy and developing a fleeting crush; after discovering Itsuki's gender, Tsubomi supports her embrace of femininity and convinces her to join the Fashion Club. She deeply respects the aloof Yuri Tsukikage; learning of Yuri's tragic past, including the loss of her fairy partner Cologne, Tsubomi motivates her return as Cure Moonlight. Key bonds include her grandmother Kaoruko, the legendary Cure Flower, who mentors her in Pretty Cure duties, and her fairy partner Chypre, who evolves from doubting Tsubomi's strength to complete trust. Romantic disappointments involve a crush on the mysterious Coupe, later revealed as her deceased grandfather's form, and a brief attraction to Olivier in a film.

Her journey spans media: In *Heartcatch Pretty Cure!*, she battles Desert Apostles like Sasorina and Dark Pretty Cure to collect Heart Seeds and heal the Heart Tree. The film *Fashion Show in the Flower Capital* sees her designing a dress to restore a prince's emotions, taking a blast for Olivier that creates a Slipknot Ponytail moment symbolizing vulnerability and strength. *All Stars* crossover films show her interacting with other Cures, including an infant version in *All Stars Memories*, highlighting her enduring optimism. A 2015 novel expands her post-series life, depicting her studying for NASA to overcome acrophobia and pursue her space botanist dream. Across all media, her core arc remains: evolving from a constrained "flower bud" stifled by self-doubt into a resilient leader embracing her introversion while fiercely protecting others' "Heart Flowers."