YOU SAID:
My sister is the most annoying person in the world kappa
INTO JAPANESE
私の妹は、世界のカッパで最も厄介な人です
BACK INTO ENGLISH
My sister is the most annoying person in the world of kappa
INTO JAPANESE
私の妹はカッパの世界で最も厄介な人です
BACK INTO ENGLISH
My sister is the most annoying person in the world of kappa
That didn't even make that much sense in English.