How do i Catch him?

Umm... Do I see the grim reaper over there? Maybe there's a item that stuns him or something.

Great hint Faidir. Also, you should use your Stopwatch whenever you feel stuck. It gives you hints like this. ("Can you give me the key?" - Ninth time: N33ERX13)

Go to a platform opposite of the ghost, and throw shurikens at him.