Chiyu Sawaizumi is a second-year student at Sukoyaka Middle School, known for her hygienic, cheerful lifestyle, strong sense of responsibility, and independent nature. Academically proficient, especially in science, and athletically gifted, she excels as the ace of her school's track and field team, specializing in high jump. This passion stems from a childhood swimming experience where she admired the seamless blend of sky and ocean, inspiring her pursuit of reaching new heights. Despite her typically focused demeanor, she possesses a distinct appreciation for puns, often laughing at wordplay others find unamusing. Her family operates the traditional hot spring inn, Ryokan Sawaizumi, where she assists and shares a close bond with her younger brother, Touji. This connection later becomes central to her aspirations. Chiyu first meets Nodoka Hanadera when Nodoka notices her dropped scrunchie, sparking their friendship. Witnessing Nodoka, as Cure Grace, injured during a battle against a Megabyogen, Chiyu convinces the hesitant Healing Animal Pegitan to lend her his power. Touched by her determination and kindness, Pegitan partners with her, enabling her transformation into Cure Fontaine, the Pretty Cure of Water, marked by the catchphrase "The two intersecting streams! Cure Fontaine!". Transforming into Cure Fontaine brings significant changes: her charcoal hair turns vibrant blue, grows extremely long, and is styled in a ponytail splitting far down, adorned with white bubbles and a pearl tiara. She dons a blue and white outfit featuring droplet motifs, a ruffled skirt, a light blue vest, and pearl droplet earrings resembling raindrops. Special forms like "Special Healin' Good Style" and "Pegitan Fontaine" introduce further alterations to her dress and accessories. Her attacks, such as "Healing Stream," utilize water-based purification powers. The transformation requires her Transformation Element Bottle, Pegitan, and the Healing Stick, involving Pegitan entering the stick and the joint activation phrase "Cure Touch!". Character development focuses on overcoming challenges. Early on, she experiences a high-jump slump, repeatedly failing to clear her personal best. This struggle forces her to confront her limitations during a tournament disrupted by a Megabyogen attack; the battle helps her accept these limits, leading to a successful jump afterward. Her dedication to hospitality surfaces when helping at the family inn. Guided by her grandmother's advice on caring for guests needing a heart "as wide as the ocean," she befriends a troubled guest, Emily Smith, strengthening her connection to the inn. A significant development arc involves her future aspirations. After winning a high jump competition, she meets rival athlete Takami Tsubasa. Chiyu reveals she intends to quit high jump after high school to focus on inheriting the family inn, which Tsubasa criticizes as lacking ambition. This prompts Chiyu to reevaluate her goals. Later, intense internal conflict arises as she desires both a professional athletic career and managing the inn. Doubts affect her jump performance and weaken her as Cure Fontaine during a battle against Shindoine. After Pegitan reassures her that both dreams are achievable, she resolves to pursue both paths, gaining her family's full support. Relationships define much of her journey. She deeply cares for Pegitan, volunteering to be his partner and nurturing him. She forms a fast friendship with Nodoka, concerned for her well-being. Initially, she clashes with the energetic, fashion-focused Hinata due to contrasting personalities, but they overcome differences, becoming close friends; Chiyu often worries about Hinata's impulsiveness but enjoys her puns. Her primary antagonist is Shindoine, a Byogen general whose values directly oppose her own, leading to recurring confrontations. In a crossover storyline, she faces a crisis of confidence, fearing she lets others down, but regains motivation with encouragement, later showing kindness by caring for an exhausted ally. Following the defeat of King Byogen, Chiyu shares a heartfelt farewell with Pegitan as he returns to the Healing Garden. She later visits the Healing Garden with Nodoka and Hinata, inadvertently causing an incident involving Nanobyogen-infected sweet buns. After the situation is resolved, she reaffirms her commitment to protecting Earth. Her name holds symbolic meaning: "Sawaizumi" combines "mountain stream" and "fountain," "Chiyu" relates to "cure," "healing," and "recovery," and "Fontaine" is French for "fountain" or "spring," consistently reflecting her water motif and healing role.