YOU SAID:
I've decided to become a fuury
INTO JAPANESE
私はお尻になることを決めた
BACK INTO ENGLISH
I decided to become an ass
INTO JAPANESE
私はお尻になることに決めました
BACK INTO ENGLISH
I have decided to become an ass
INTO JAPANESE
私はお尻になることに決めました
it is unlikely that this phrase will ever reach equilibrium