Trying to find an NES game

[wayjurn]

I remember probably 8 or 9 years back that my friend had this NES game. I don't remember what it was called, but I sort of remember what it was about. You played a boy with a yoyo, and your father or grandfather was a scientist who owned this big island shaped like a crescent moon. The focus of the game was to explore caves and knock out all this undead creatures (I specifically remember an undead ostrich-type creature) with your yoyo and other weapons.

Does anyone know what I'm talking about? What was the game called?