Shiranai machi

Yuji Itabashi works for investigating to make maps. One day, a woman who he never know visits his room. She says she came to visit Goto, a boyfriend she lived together, and come to pick up the thing that she left behind. Later on, Yuji's friend, Kosuke Nishida; a junk dealer, who was with Yuji when the strange woman came, starts to make a fuss saying he saw Ghost in the room while he was alone. What was the Ghost the Nishida saw?