While your specific query aligns with the adult publication, the term "Kokeshi" more broadly refers to traditional Japanese wooden dolls from the Tohoku region, which are categorized into 12 official styles

Her voice softened. “My mother had a kokeshi,” she said. “We lost her in a move. She used to keep letters and a charm in the base. Her name was Hikari, too.” She sat on the stool as if she might emerge from a memory. “We look for her still.”