After heading south to investigate the place known as Tomato Heaven,
Maru and Kiruko head back to Tokyo via a "ferry". But they are ambushed
at sea by one of the man-eating Hiruko monsters. This specific beast is
amphibious, making him extremely deadly as he can easily take cover in
the sea. Meanwhile in the school, Tokio, with the help of his classmate
Kuku, uncovers a frightening secret. Maybe life is not what it seems at
all. Maybe those who are inside the walls are not in heaven. And maybe
the walls are there to keep them all inside!