Due to a sudden health problem, Akane is admitted to the hospital for a while and finds out that she shares her room with a younger girl in a coma.
On the first night together, however, Akane wakes up and is surprised to see
the girl staring at him by the bed, jumping and apparently healthy.
The two had entered young Yui's comatose mind.
A vast and dangerous world that opens like a book for the pair and makes, as they descend to the bottom, the charms and mysteries become increasingly cruel truths.