The Fleeing Ghost looks like a typical ghost with one eye in the middle of his forehead, which can be found in The Ghost World. The Triangle Kerchief Effect can be obtained by interacting with him.
He moves quite fast and flees from Madotsuki which obviously gave him his name. The easiest way to catch him would be with either the Stoplight or the Cat Effect. It also react normally to the Knife Effect like most NPCs.