Aika is a beautiful white-skinned young woman with waist-length light-brown hair that is tied at the back of her head with bangs hanging on the left side, light blue eyes, red lipstick and rather large breasts.
Aika's main outfit is a long sleeve red jacket with white at the end of the sleeves, a white collar with a green bead, her golden bustier under her jacket, a tight red skirt, red high heels and white panties. When she activates her bustier, her appearance changes to Shivie Aika; a tanned-skin woman with long blue hair, a white bra and panties. However, she also keeps the collar and the shoes in this form. At the beginning of the first episode of Agent Aika, she wears an orange bra and orange panties. When infiltrating the Delmo base, she wears a gray tube top and blue panties.
Aika has shorter hair that she wears down where part of her hair is braided on one side.
She wears a long-sleeved short red dress and white thigh high stockings. She also wears white panties.
During the beach episode, Aika wears a purple ome-piece swimsuit.
Aika wears a white shirt and a blue tie underneath a long-sleeve red jacket and a black microskirt. Her hair is longer, reaching her shoulders, and worn down without a braid.
Aika is 16 years old in this series who starts her job as a salvager by her foster parent. Later, she goes to school and she is recruited by Eri Shinkai to go on a expedition to solve the mystery of Karen Minamino's past.
Taking place three years later, Aika and her two friends continue to hang out together at a restaurant. She is later roped into another adventure by Eri Shinkai to find the missing students of their school. She carries a tranquilizer gun, and later, a submachinegun-like weapon loaded with non-lethal bullets. Here we discover that she has a special power that may have a connection with Lagu.
Aika is a salvage agent, a person who digs up submerged artifacts from the cities below. She works for a small company run by Gozo Aida and takes on fairly dangerous jobs. In the first story, she and Rion Aida (Gozo's daughter) search for material called the Lagu.
- The name Aika means "indigo" (藍) (ai) and "flower" (華) (ka).
- Aika's surname Sumeragi means "emperor" (皇).
- Aika is shown to have different eye colors in different series: