A mysterious Nigerian girl around Jess's age who only Jess can see and interact with, leading to adventures that blur the lines between imagination and reality. Her true nature and connection to Jess remain ambiguous.

Jess's mother, who was born in Nigeria and moved to England. She has a sometimes strained relationship with Jess, influenced by her own upbringing and cultural heritage.

Jess's father, an Englishman who tends to be calmer and more patient compared to Jess's mother. He attempts to maintain a more open communication style with Jess.

Dr. McKenzie’s daughter and Jess's friend, known for her talkative and lively nature, which contrasts with Jess's reserved demeanor. Despite initial belief in Jess's stories, she becomes wary of TillyTilly.

A psychologist who provides a supportive environment for Jess to share her thoughts but grows concerned about her mental health as her behavior changes.

Jess's grandfather in Nigeria, deeply rooted in both Christian and traditional Nigerian beliefs. He forms a close bond with Jess during her visit to Nigeria.

A classmate of Jess's who is part of the popular crowd and occasionally bullies Jess. They have a complex relationship fraught with tension.

Jess's cousin on her father’s side, who often seeks attention from adults and considers Jess to be odd. Their interactions are marked by mutual annoyance.