YOU SAID:

I have a cat that runs behind its tail

INTO JAPANESE

私はその尾の後ろを走る猫がいる

BACK INTO ENGLISH

I have a cat running behind that tail

INTO JAPANESE

私はその尾の背後にある猫を持っています

BACK INTO ENGLISH

I have a cat behind that tail

INTO JAPANESE

私はその尾の後ろに猫がいる

BACK INTO ENGLISH

I have a cat behind the tail

INTO JAPANESE

私は尾の後ろに猫がいる

BACK INTO ENGLISH

I have a cat behind the tail