She takes a few steps―― again, she's crushed along with a scream. Death. For some time now, this process has repeated. Waking up in an unknown room, Kyouya finds that he cannot move his body. Calling for help but receiving no response, he spends months, years, unable to do a thing; when a girl that calls herself 'human' appears. Begging the girl to take him outside, Kyouya finds naught but a desolated world left behind. Before the dumbfounded Kyouya, the girl called 'human' says: "On this Earth, other than I... and you, no humans remain." All the plants and fauna have perished too, she says. Unable to accept the words of the 'human' who has embarked on a certain mission, Kyouya is carried away by her. So begins the endless journey of Kyouya and the girl called 'human'.