Saeko Busujima (毒島 冴子, Busujima Saeko) is a third-year student at Fujimi High School with dark violet hair and bright blue eyes. As the president of the school's kendo club Saeko carries a bokken (wooden sword). Saeko is introduced as a calm and collected girl with pride in her skills; she kills an infected student out of mercy. Her father is abroad somewhere for a martial arts tournament.
Saeko confides in Takashi that she was once almost sexually assaulted, but was able to fight back with her bokken and ended up breaking several of the attacker's bones before the police came. Although Takashi says it was self-defense, Saeko counters saying that it is her "raw nature" to take pleasure in inflicting pain and, in that way, she is no different than one of the zombies. She struggles with this part of her character and even considers giving up to "them", until Takashi helps restore her confidence.
Saeko initially uses her bokken to fight, but upgrades to a katana when they stop at a shinto temple and then again at the Takagi estate. After the group visit a police station, Saeko starts carrying a Beretta 92 Vertec handgun on her thigh as a secondary weapon.