Kimi ni shika Kikoenai
Nobody Can Hear Me But You
きみにしか聞こえない
A timid schoolgirl imagines owning the ideal cellphone in her head, but one day, there is a connection; the phone rings in her head, and someone is on the line!
Note: Tsuzuki Setsuri also did a manga based on the same novel.
(Source: MU)