After they had been led off the boat by siren’s magic song,
Yusuke soon finds out that his friend Tetsuo is not what he used to be; He started attacking people at the sight of blood.
Later, Yusuke learns that after Tetsuo had awaken after the zombie island incident he is unable to sleep, hearing the voices of the ghost girl in his head, telling him to devour…and also that Tetsuo may be dying as well, probably due to the ghost.
Yusuke is devastated by all this, trying to find any way to help his friend, but not seeing any leads.
But even in these dark times, the boy keeps moving forward, hanging onto the single hope that the bond of their friendship will pull them through.