A creature that resembles the Ghast from Minecraft is the Noppeppo, a Japanese yokai that has almost no historical explanation for its existence. It merely appears in an Edo Period yokai scroll, with a white blob for a body and a wrinkly face.
The Noppeppo is passive and almost harmless. It simply travels around leaving a rotting stench behind it, akin to rotting meat. It is believed that those who consume the flesh of Noppeppo will be granted eternal youth, ironically. I can only imagine someone poisoning themselves if they consumed the flesh of a creature that smells like it’s rotting. Nonetheless, people who believe so have come to consider the Noppeppo a delicacy.
The motives of this wandering creature are not fully understood. It usually travels alone, but may sometimes be seen in groups, and their purpose may never be known.
Creatures like this without a history or big impact are what surprise me about Japanese tales. It really looks like just someone’s imagination being drawn to paper, and it doesn’t even look that great, but it still manages to attract so much attention and have a background created for it.