Asa Motegi is a cheerful and outgoing high school classmate of Sora Kashiwagi and Tazuki Kamiya. She has maroon hair often in pigtails, pink eyes, and stands 149 centimeters tall. Her typical outfit is her school uniform: a blue blazer, pink vest, blue bow-tie, black skirt, black stockings, and pink hair clips.

Exceptionally kind and open-minded, Asa embodies the "Nice Girl" archetype, earning the title of an angel from Sora and Daichi Tachiaki for her helpful, compassionate nature and positive demeanor. She enjoys listening to others. Despite a general fearlessness toward insects, she possesses a severe phobia of lizards.

This phobia shapes her initial reactions to the dragon Isao, whom she mistakes for a giant lizard. Her petite stature belies extraordinary physical strength, allowing her to effortlessly lift heavy objects like bookshelves or carry adults. This strength intensifies dramatically when she is frightened or panicked, nearly destroying her room upon encountering Isao.

Observing Isao's gentle behavior helps Asa overcome her terror. She forms a close bond with him, adopting and naming him Isao, marking significant progress in confronting her phobia. Within her friend group, known for mutual warmth and trust, Asa gives affectionate nicknames like "Sora-chan," "Tacchan," and "Dai-chan." Her endearing qualities lead Sora to wish she were his little sister.