So I did as he ordered and he came back and put a collar on me that locked on. He sat down on the stool and told me to finger myself until I was told ... could stop. I said, "Yes Sir" and started masturbating while he watched and took more cell phone photos. Customers came and went and Keith waited on them, Rung up the purchases while I continued to finger myself practically right under the cash register.I was wet! This went on for about a half hour and I had several orgasims but I put my left. Arushi opened the door in surprise and asked me the reason for my sweating. I told her that I was not very comfortable with the algebraic equations and I needed her help urgently. She asked me to come in and locked the door behind us as she knew her brother would not be coming in tonight.She was wearing a tight white top and blue shorts. The top traced the curvature of her breasts and the fact that she was not wearing a bra was revealed by her nipples poking through her shirt. I realized I was. She said. ‘Jimmy, it is ok. I am sorry.” She had dropped her book when she came back in and saw me. So she bent over to pick up her lesson book..As she did, her night came up to the butt, and I saw my young sisters pussy in plain view. She had no panties on. I cleared my throat and said “guess we are both even now.’ She turned and realized what she had just done. No words were spoken. She walked to the bedside and just looked at my hard cock. She reached forward and started to jack it up and. I let her calm down for a while, grabbed her PJ and wiped her pussy clean. I grabbed her thighs and slid her down the sofa closer to my pelvis, “It’s been a while, please be gentle” she said. I had one of those devilish smiles on my face, I grabbed my cock and started teasing her by slapping it on her clit and all over her pussy. I leaned forward a started sucking on those massive tits of hers, her nipples were as hard as my cock, I kept switching between the two nipples.Looking up to her face.