YOU SAID:
The cat killed the mouse which killed the ant which killed the cat.
INTO JAPANESE
猫は、猫を殺したアリを殺したネズミを殺した。
BACK INTO ENGLISH
The cat killed the mouse that killed the ant that killed the cat.
INTO JAPANESE
猫は猫を殺したアリを殺したネズミを殺した。
BACK INTO ENGLISH
The cat killed the mouse that killed the ant that killed the cat.
That didn't even make that much sense in English.