Help find a really old manga

Help me find an old smut manga where the young FL wants to work at a brothel to pay debt, the ML that is a manager there then takes her to the back through an intimate test to scare her. But she insist so he teaches her different ways of intimate intercourse. In reality, he actually has always liked her and doesn’t want her to sleep with any client.

I believe the FL have light colored short hair, and ML dark short hair. But I’m not 100% sure. It’s old manga so black/white pictures