YOU SAID:
I wanna sit on my sisters lap and pee
INTO JAPANESE
姉の膝の上におしっこをしたい
BACK INTO ENGLISH
I want to pee on my sister's lap
INTO JAPANESE
妹の膝の上でおしっこしたい
BACK INTO ENGLISH
I want to pee on my sister's lap
Come on, you can do better than that.