Black★Rock Shooter (OVA)

Mato Kuroi meets Yomi Takanashi on her first day of junior high school, and they quickly become friends. Their friendship is marked by a blue star-shaped cell phone charm that Mato gives Yomi, mirroring her own. As they enter their second year of school, Mato's class is rearranged, causing her to spend more time with Yuu Koutari from the basketball team. Yomi seemingly disappears, and her connection to Mato is later linked to the Blue Star, a cell phone charm that also ties into Black★Rock Shooter's quest to defeat the Dead Master.