Yū Sumio is the protagonist of the narrative. She appears as a teenage female student with brown eyes and neck-length brown hair. Her attire consists of a standard school uniform, a ribbon tie, and a hairclip.

The story focuses on her experiences during an unexpected zombie outbreak at school. Isolated on the rooftop with other surviving classmates after their peers transform, she faces limited rescue prospects. She collaborates with the group, utilizing their knowledge and resources to devise an escape plan.

Her actions include documenting the zombie phenomenon through filming, indicating a pragmatic approach. Her interactions throughout the survival ordeal emphasize group coordination and strengthening interpersonal bonds among the survivors. The narrative concludes on a cliffhanger before their ultimate fate is determined. No additional background, development, or appearances beyond this scenario are documented in official media.