Appearing and disappearing unpredictably; elusive—used for someone or something that turns up unexpectedly and is hard to pin down.
彼はまるで神出鬼没で、連絡をするとすでにどこかに移動していることが多い。
He's like a ghost—appearing and disappearing; when you try to contact him he's often already moved elsewhere.
その猫は夜になると神出鬼没に現れては町を徘徊する。
That cat appears and disappears at night, prowling through the town.
神出鬼没の探偵という設定が人気を呼んだ。
The concept of an elusive detective who appears unexpectedly became popular.