YOU SAID:

Underwear should be worn on the inside

INTO JAPANESE

内側に下着を着用する必要があります。

BACK INTO ENGLISH

You need to wear underwear inside.

INTO JAPANESE

中の下着を着用する必要があります。

BACK INTO ENGLISH

You need to wear underwear in.

INTO JAPANESE

下着を着用する必要があります。

BACK INTO ENGLISH

You need to wear underwear.

INTO JAPANESE

下着を着用する必要があります。

BACK INTO ENGLISH

You need to wear underwear.