Yuna Amasato is a college student and the younger twin sister of Minael. Together, they form the duo known as the Peaky Angels. In civilian life, both sisters share nearly identical appearances and personalities, making them difficult to tell apart. They typically present themselves as innocent and sweet around others but exhibit rude and mean-spirited behavior privately, often speaking negatively about people behind their backs. Despite this, they display genuine care for their teammate Tama.

As the magical girl Yunael, she possesses short, light brown or golden hair curling inward at chin-length, distinct purple eyes with cross-shaped pupils, and wears a dark blue and white ruffled dress with a lacy white collar tied by a black ribbon. A single feathered wing protrudes from her back, and a floating halo hovers above her head. A ribbon on her right ankle differentiates her from Minael, who wears hers on the left leg. Yunael's magical ability allows her to transform into any living organism, regardless of size, shape, or species, provided it is biologically alive. This transformation requires her to memorize the target creature's appearance completely; incomplete details prevent the magic from working. Upon transforming, she gains the physical form of the chosen being but retains her own physical capabilities and cannot replicate the creature's innate abilities or special powers. Vocal mimicry is possible during transformation. The halo enables flight. Her standard equipment includes energy pills—consumable items that temporarily enhance strength, endurance, and durability for approximately thirty minutes, though overuse risks heart failure.

Yunael operates under Ruler's mentorship as part of Team Ruler alongside Minael, Swim Swim, and Tama. While outwardly loyal, she harbors deep resentment toward Ruler's bossy attitude and celebrated Ruler's death with Minael. Her relationship with Swim Swim evolves from viewing her as "Ruler's little slave" to respecting her as a leader. The twins frequently collaborate in pranks and battles, their magic complementing each other; Yunael cannot reach her full potential without Minael. They maintain a close bond, consistently fighting together and prioritizing each other's safety.

During a confrontation, Yunael transforms into a replica of Sister Nana to deceive Weiss Winterprison, stabbing her in the heart. Weiss Winterprison retaliates by slamming Yunael against a wall, causing her immediate death. Her demise profoundly affects Minael, who becomes more ruthless afterward to avoid repeating past mistakes. In non-canonical scenarios, she demonstrates broader capabilities, such as interacting with conceptual entities and resisting conceptual manipulation, though these feats fall outside established continuity.