Go left, talk with this girl, she tells you, you can't defend yourself and you should learn the combat.
Then go through the crack here
And walk to the right until you see this girl. By interacting with her, you start combat.
After you hit her, she retaliates. You have to time your dodge and conserve enough stamina to be able to dodge.
The timing window is extremely short and you have to dodge the attack animation, which happens almost instantly after the Warning disappears. Finding out the perfect timing is difficult. Beat her, and you can again talk to the woman left of your house and start exploring.
After you talk to her, she allows you through and you can choose the 4 stages. Talking to the other girls telly you what they want from you in order to have sex with you.