On a summer afternoon under the blazing sun, Aki, a boy who’s often bullied, decides to confess his feelings to his childhood friend, Yui.

However, on their way home, Yui suddenly disappears. Even though they had been walking together, she vanishes without a trace.

But then, Yui appears before him once more.

"I’ve become a shadow." As long as there was a shadow, she could come and go freely — through the ground, the ceiling… even through people’s bodies.