Agnes Boulange is a roaming puppeteer who arrives in Ert'Aria, staging circus acts with her controlled automata puppets. She encounters Leicester Maycraft and his companions during a meteor shower, subsequently finding shelter with their adventurer group, Clan Oasis. Agnes came to Ert'Aria seeking her mentor and mother, Mise Altoise, creator of the automaton Minette. As Mise Altoise's apprentice, she holds knowledge about automata and aids Leicester in understanding Minette.

Agnes presents a cheerful, carefree, and curious disposition, speaking her mind directly. Her positive demeanor uplifts others, though she harbors inner fears connected to her search. Her intuitive nature prompts spontaneous actions, sometimes without deep forethought. She exhibits a pronounced fondness for desserts, especially cake, which she finds hard to resist. During her time with Clan Oasis, she develops romantic feelings for Leicester, joining several others attracted to him.

She is accompanied by Tango, a talking cat automaton she created. Tango participates in her performances and acts as her confidant, distinguished as her sole creation possessing independent consciousness and speech. Physically, Agnes has ochre hair styled in pigtails, pink eyes, stands 150 cm tall, and has measurements of 76-57-80.

Agnes's journey involves integrating into Clan Oasis while persistently pursuing her mother's trail. She provides crucial expertise on automata throughout the group's adventures, including clashes with figures like Aberdeen Roland who target Minette's core energy. Her path balances her personal mission with newfound responsibilities and kinship within the clan.