Why Don't You Lift Up That Skirt And Show Me Yours, Sister?

My brother started looking for people. He seems to be looking for a woman he fell in love with at a mask party. The only reference he has of that beautiful woman is only a small mole on the inner part of the thigh. And that woman is ... Ne-chan !? A love story given by a MC who can't be honest! Do not be fooled by the title! This is a pure love!