Backyard Bottomslash (バックヤード・ボトムスラッシュ, Bakkuyādo Botomusurasshu) is a 28-year-old bank worker and a victim of the Los Angeles BB Murders.
Bottomslash was drugged before her death, much like Quarter Queen, whose death occurred nine days earlier. Through her murder, the killer wanted to find out if a human could die of an internal hemorrhage without rupturing any organs. This experiment was conducted by drugging and then beating Backyard Bottomslash's left arm without breaking the skin. When this did not work, her right leg and left arm were cut off, and she died from exsanguination.
Her right leg was later discovered in her bathtub, and the left arm was not found at the scene. Two wara ningyo were found nailed to the walls in a similar manner to the other two previous murders.
- Backyard Bottomslash's initials, B.B, are a reference to Beyond Birthday.