Before the outbreak, Rei was dating Hisashi as a final attempt to make Takushi notice her after many attempts before this was the last one before she would finally give up on Takushi only for the apocalypse to strike after the death of Hisashi she grows into an unhealthy one-sided realasonship to a possessive nature around Takushi it's her way of coping

Most of the EP is taking place during The Initial outbreak so it's a realistic take on how someone would act in an apocalypse so that would be up to you as it's happening around you