YOU SAID:

i have at least fifteen fish in my underpants right now

INTO JAPANESE

私は今、パンツの中に少なくとも15匹の魚を飼っています

BACK INTO ENGLISH

I now have at least 15 fish in my pants

INTO JAPANESE

ズボンの中に少なくとも15匹の魚がいます

BACK INTO ENGLISH

Have at least 15 fish in your pants

INTO JAPANESE

ズボンに少なくとも15匹の魚を入れてください

BACK INTO ENGLISH

Have at least 15 fish in your pants