This oni is irregular. It looks like an amphorous mass with 10 eyes visible on it. The Blob Oni is relatively slow and sluggish.
The blob oni is found in the oni room. On the wall behind it is the front door key. The player must take advantage of the oni's slow speed to obtain the key and flee. During the Blob Oni "chase", the menu can be accessed and the game can even be saved, which is not possible during other chases.
The blob oni can be seen in the oni room in Version 6, moving slowly around the cage, but cannot be interacted with and does not chase the player.