Sumika is a librarian who works in Glie with her apprentice, Nemu. Like the other Haibane, Nemu invites Rakka to work with her to see what career would best suit her after arriving to Old Home. Sumika takes a liking to Rakka and teaches her the history of Glie through the library's large amount of artifacts and books on the origins of the city and what lies beyond the walls. Before Rakka arrived in Glie, Sumika and Nemu worked together on many projects and built a close friendship through exchanging stories about the origin of the Haibane. Sumika eventually retires after becoming pregnant and leaves the majority of the library's responsibilities to Nemu.