Eun-sook

A girl who discovers she's an ESPer by sheer accident of encountering a guy named Dee who only she can see. 

She practices her abilities with him, which take a great deal of concentration to even form any coherent thoughts to communicate with Dee.

Her mental projection manifests as a bright orange spark, which is the one thing Dee is actually able to see in the void he's stuck in.

Their dynamic is likely to change a little once Dee syncs with the third dimension...