Mana Aida, known as Cure Heart, leads the Doki Doki! Pretty Cure team. She excels as a second-year student and student council president at Oogai First Middle School, admired for her athletic skill, academic success, and innate leadership that builds trust with peers and adults. Her personality blends cheerfulness, impulsiveness, and a powerful sense of responsibility, driving her to prioritize others' needs instantly, sometimes acting before weighing consequences. Her signature "Kyunkyun" catchphrase reflects her focus on love and emotional bonds.

A defining childhood trauma involves her pet dog, Marshmallow (Maro), killed by a car while she visited her hospitalized grandmother, leaving lasting emotional scars. Her grandmother, Bando Isuzu, reappears transformed as the fairy Bebel in the movie "Mana Kekkon!!? Mirai ni Tsunagu Kibō no Dress."

In this movie, Mana receives a wedding dress worn by her mother and grandmother. Contemplating her future, she meets a mysterious man named Marsh who transports her to the past. There, she reunites with her grandmother and Maro but finds friends Rikka and Alice missing due to altered memories. Marsh traps people within film reels, forcing them to relive past memories endlessly. After her fellow Cures are defeated and imprisoned, Mana discovers Marsh is actually Maro, manipulated by a sentient clarinet. This clarinet weaponizes discarded objects and manipulates memories to erase futures.

Confronting her grief over Maro's death with encouragement from her grandmother and friends, Mana achieves emotional resolution. This unlocks Engage Mode, a powerful transformation resembling a bridal gown, enabling her to defeat the clarinet. The movie ends with a glimpse of Mana's future wedding where the Cures appear in formal attire, symbolizing restored hope.

Key relationships shape her character. She shares deep childhood bonds with Rikka (Cure Diamond) and Alice (Cure Rosetta), often protecting them in youth. She initially idolizes Makoto (Cure Sword) before forging a partnership. Other vital connections include her fairy partner Sharuru; Regina, a friend formed despite early conflict; and Aguri (Cure Ace), who mentors her through self-doubt.

As Cure Heart, her design features heart motifs. Transformations include a standard pink battle dress, winged Parthenon Mode, and the bridal-inspired Engage Mode. Her abilities center on love-themed attacks like "My Sweet Heart," showcasing resilience in battle, frequently rescuing allies or persevering through setbacks.