On the Day I Descended the Mountain, My Beautiful Senior Sisters Gave Me Three Marriage Contracts

The day you descend the mountain, your beautiful senior sister gives you three marriage contracts and tells you to choose one of the women as your wife. But you already have a girlfriend! What kind of situation is this?! Before you leave, your beautiful senior sister looks worried and hesitates to speak. Looking at the lush green bushes and old trees nearby, she insists that you go home and take a look first. So you take the expensive crystal necklace you bought for your girlfriend and head to the marital home your parents bought for you. But then the indecent sounds coming from inside the house reach your ears...