fantasy with younger sister (part 1)

Hi friends, I am Raj, I live in the join family. My mother, father and younger sister live with me.My sister has a very sexy figure, any boy will go crazy after seeing her breasts. My sister is 19 years old but she enjoys teasing boys. So the story starts from here 4 years ago When I was in 1st year of college, I was talking to my girlfriend on video call in my bedroom.And the door was not locked, I was masturbating. My mom knew that I do it, but I did not notice that my mother was at home. But I did not know that my sister had come home from school and she saw me masturbating from behind. And Mom had gone out to a party at her friend's house and Dad was out of town mostly due to business so it was just Payal and I at home.As soon as I got free from the video call, I felt that there was someone behind the distance who was watching me masturbating. I first freshened up and went to the hall and saw that my sister had come back from school.She was doing her homework and thought I didn't know she was watching me while I was in the bedroom.I also asked her ignorantly when did you come, she said half an hour.I said ok mom has gone to a party, she will come back at night, she has prepared the food, we have to finish our homework quickly and have lunch.Then she also finished her homework and changed into a sexy top with a deep neckline and was not wearing anything else inside. We ate together and while eating Payal asked me, brother