"A typical good student lauded for her outstanding performance. Although the education and training she has received growing up in the Foundation are of top class, she finds everything in the outside world novel."

Playable character of Reverse:1999 and also a friend of Vertin. She has orange hair, green eyes, and wears the Foundation's standard costume consisting of white dress and white gloves. She uses a glass pen to cast Arcanum and attacks enemies.

Sonetto is voiced by Rae Lim in English and Uchida Shuu in Japanese.