Gomu Wo Tsukete To Iimashita Yo Ne... -

While it literally means "rubber" or "eraser" (derived from the Dutch word gom ), in this context, it is the standard slang for a condom.

This is the uchi-soto (inside-outside) principle gone rogue. In Japanese culture, you are expected to read the air ( kuuki yomenai – KY). Having to repeat an instruction is considered a social failure for the listener , not the speaker. gomu wo tsukete to iimashita yo ne...