Yumiya Akashima, a former high school softball team captain, developed a hidden smoking habit due to leadership stress. This secret was exposed only when tournament officials discovered cigarettes in her belongings, leading to her team's disqualification from national qualifiers. The incident ignited lasting resentment from teammate Kaoru Ikari over the lost opportunity.

Amidst a sudden zombie outbreak at their school, Yumiya acted swiftly to save Kiriko Tounuma from an attack. She joined a group of survivors fighting to escape the overrun building. When the science club created a bomb to breach the school gate, Asayo Takamori retrieved it but found herself trapped by zombies with no time for safe placement. Takamori shouted for Yumiya to throw her a lighter to ignite the bomb immediately. Despite being long out of practice, Yumiya executed a perfect throw. Takamori caught the lighter and sacrificed herself by detonating the bomb, blasting open the gate so Yumiya and the others could flee.

Yumiya escaped alongside Kaoru Ikari and Shizuka Murasaki, heading towards a nearby mall. Her ultimate fate remains unresolved beyond this point.