In a world still healing from a devastating virus, student teacher, Haruki Takana finds himself in the middle of a crisis. On the tenth anniversary of the outbreak, a routine school assembly descends into chaos when an emergency evacuation has been announced and the students are given 24 hours to get to the pier, where a boat, there only way of survival, is waiting for them. Students erupt in panic as they confront their nightmarish reality that just outside the school gate, a hoard of the undead are waiting for them.

Amidst the panic, two students stand out. Aiko Sato, the unflappable student council president and Yuki Nakamura, a timid first year with gripping fear sinking in her heart.

Haruki, along with Aiko's determination and Yuki's fragile state, aim to navigate their way through the 24 hours and achieve safety. Relying on their own strengths and unexpected allies, will they make it to the pier withing the 24 hours or will a haunting past claim them?