On the first day of a new school year, first-year student; Hayato Najimi sees an unconscious older student from his school, in a alleyway. He takes the male student to his house and fix him up, when the male student wakes they found out that not only do they go to the same school, he found out the male student's name is Ryousuke Ichigo. Son of a Yakuza Clan. The two make small talk and get along really well. Then the Apocalypse hits their school, turning the other students and teachers into walking corpses. And Ryousuke shows his true colors for the boy he loves.