YOU SAID:

I found my sister in a tree eating a fish

INTO JAPANESE

私は、木の中で、魚を食べている妹を見つけました

BACK INTO ENGLISH

I found my sister eating fish in the tree.

INTO JAPANESE

私は妹が木の中で魚を食べているのを見つけた。

BACK INTO ENGLISH

I found my sister eating fish in the tree.