After school I worked as a volunteer for a NGO. We were mostly young guys and some girls.
There was this one petite young girl, 1,55 meters at best with huge natural tits (D or E). She wore the smallest size of the uniform polo shirts, but because her boobs were that big her shirts were always like crop-tops. Obviously she enjoyed a lot of attention from all the young guys and she really loved it.
There was a room with a couch and a TV where we often relaxed when there was nothing to do at the moment. The couch was quite small and with 4 guys and the girl sitting on it there was no place left for me to sit when I entered the room.
She immediatly suggest that we could share her space. She was leaning against the backrest and spread her legs, suggesting that I should sit between her legs using her as my backrest. I agreed and sat down. At first I was too shy to lean back but after a while I got tired and relaxed. My head was resting on her huge soft boobs using them as a pillow. I was feeling her tits all over the sides of my head, it was an awesome feeeling. The other guys seemed to be a bit jealous.
Lying on her tits for about 20 minutes I had the time of my life
She wanted to get up to grab something to drink. When she came back all the guys told her that they would like to share their spot with her. But she said that because I was using her as a pillow I had to "endure" her sitting on me now.
She sat on my lap right above my penis. I could feel her moving her ass slightly all the time rubbing on my dick and I instantly got a boner. Her movements were really subtle so I think it was not obvious for the other guys. They were all looking at the TV and I gently groped her ass from behind. Unfortunately we had to get back to work shortly after.
I noticed that she was doing similar things with other guys, she almost never used a chair for herself but always sat on someones lap. And her boobs were more often used as a pillow than the actual pillows.
There was rumours that she was having sex with some of the guys. One day I took the courage to ask her if she'd like to go for a drink after work with me. When we met I asked where she wanted to go, instead of a bar she suggested that I should come to her place. She lived in a student dorm, right when we entered her room she said "I know what you really want" and pulled my pants down. She was really good at giving head and I got to see her great big boobs naked and cum all over them.
Over the next months we met a few times and fucked. I talked to some of the other guys, there were at least 6 of us fucking her regularly. Unfortunately she then went to a different university.