Acidic Blood or Acidic Ooze as it's known in the Nightmare Edition is an item that appears in Corpse Party D2: Depths of Despair and it's remake. It's a bucked made out of glass and filled with corrosive blood (green liquid in the remake).
Much like in the original, to get this item you need to first have the glass bucket, but, unlike the original, to fill it you first need to enter classroom 2-3 after using the rusty key. The ghost will ask you to fill the bucket and after filling it with the green ooze Ayumi will immediately hand her the bucket.
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Acidic Ooze is one of the items that was renamed in the remake of Depths of Despair.
It's content was also changed to match the continuity better: from blood to green ooze.