Towa Akagi, originally Princess Hope Delight Towa of Hope Kingdom, is the younger sister of Prince Kanata. As a child, she admired her brother and dreamed of becoming a Grand Princess, a goal achievable only by a Princess Pretty Cure. This ambition led her to accept an offer from the witch Dyspear, who manipulated her aspirations. Dyspear kidnapped Towa, imprisoned her within the Forest of Despair, erased her memories, and transformed her into Twilight, a high-ranking member of Dys Dark. As Twilight, she served as Dyspear's second-in-command, believing Dyspear to be her mother. She dismissed dreams as illusions, denounced the Pretty Cures as "fake princesses," and exhibited ruthless, vain traits. Utilizing black Dress Up Keys, she amplified the power of Zetsuborgs summoned by Dys Dark's generals and wielded a violin as her weapon. Her Twilight appearance featured long silver hair cascading in four coiled locks, striking red eye makeup, a mask, and a dark grey mini-dress adorned with a wing-shaped overlay and a gold butterfly ornament.

Initially presenting a veneer of courtesy, Twilight swiftly turned hostile when feeling threatened, especially targeting Cure Flora (Haruka Haruno); she attempted to destroy Flora's treasured book to crush her spirit. In battle, she nearly defeated her brother Kanata, failing to recognize him due to Dyspear's brainwashing. However, the combined efforts of the Pretty Cures and Kanata's violin playing, which stirred their shared childhood memories, purified her. This shattered Dyspear's control, restoring her true identity as Towa and freeing her from despair.

Following purification, Towa adopted the surname Akagi, meaning "scarlet castle," reflecting her royal heritage and theme color. Struggling to adjust to life on Earth, she displayed naivety and social awkwardness, unfamiliar with human customs like attempting to purchase a castle and maids. She enrolled at Noble Academy as a first-year student, rooming with Kirara Amanogawa. Their relationship faced early challenges due to Towa's inexperience and Kirara's modeling career. Despite this, Towa remained inherently kind, courageous, and observant, having learned to detect deception from her experiences with Dyspear. She forged close bonds with classmates Haruka, Minami, and Yume. Minami helped her overcome her lingering fear of darkness—a remnant of her time as Twilight—teaching her to rely on friends for support.

Towa ultimately became Cure Scarlet, the Princess of the Flames, introducing herself as the "Princess of the Crimson Fire." Her transformation granted fire-based powers and altered her appearance: her hair turned light pink with a magenta ombre, she sprouted feathery wings behind her ears, and wore a gold tiara studded with ruby gems, a ruffled off-white dress embellished with red feathers, and gold accessories. She could also access enhanced forms like Mode Elegant Phoenix and Mode Elegant Sun, featuring extended skirts, additional regalia, and altered color palettes. As Cure Scarlet, she fought alongside fellow Pretty Cures, wielding her violin and harnessing Dress Up Keys such as Scarlet, Phoenix, Sun, and Hanabi (Fireworks). A key moment saw her utilize "warm feelings" learned from Yume to liberate her friend from captivity.

In the film *Eiga Precure Dream Stars!*, Cure Scarlet collaborated with the Kirakira Pretty Cure a la Mode and Witchy Pretty Cure! groups to aid Sakura from Sakuragahara in rescuing her friend Shizuku and defeating the yokai Karasutengu. The plot involved interdimensional travel and joint battles against entities stealing beauty across worlds.

By the series' conclusion, Towa reconciled with Kanata after his temporary memory loss. She eventually returned to Hope Kingdom, succeeding her mother as queen. As an adult queen, she wore a white and red regal gown and a tiara with three red jewels, her hair grown longer, embodying her fulfilled dream of leadership and her journey from brainwashed antagonist to benevolent ruler.