This happened just after I got married to an Asian girl. Her parents and two youngest sisters moved in with us. The sisters were 16 and 14. Angie was the 14 year old and she was extremely attractive.
She noticed that I was very interested in her body which was fully developed with almost B cup breasts. She decided to tease me by cutting off a couple of her T shirts so they just barely came down below her breasts and she would walk around the house like that, wearing no bra.
She would bend over to pick up something off the floor, but bend from the waist while I was behind her, giving me a full view of her bare breasts hanging down inside the loose t-shirt.
I would get so horny that I would go to my room and masturbate on the bed. Then one day I noticed Angie was on the deck outside my bedroom window carefully spying on me while I masturbated. I pretended not to notice.
One time Angie was sleeping on the floor in the bedroom with my wife and I because we had company. After my wife was asleep I pulled the covers off me and started to stroke my cock while lying on my back. Out of the corner of my eye I noticed that Angie had carefully propped herself up on one elbow so that she could see over the edge of the bed and watch me masturbate. Again I pretended not to notice, but it made me super horny.
It seemed like Angie and I were often alone in the house together and she always took the opportunity to 'accidentally' show me her perfect breasts, and sometimes would find an excuse to rub them against me, which made me even hornier.
We never did do anything together, but I did catch her masturbating once by peeping through her bedroom door which she had left open a crack. She was humping a pillow on her bed and when she came she disguised her heavy breathing and moans with deliberate coughing.