My extremely limited bi- experience.

The following story is true. The names have been changed.
When I was 13 me and three of my friends were playing cards on my bedroom floor one afternoon. It was a game called Strip Jack Naked and involved having to give cards to other players if you turned over a JQKorA. Anyway we were alone in my room and someone suggested we actually play 'strip' Strip Jack Naked. It sounded like a laugh. So we were doing that and all got down to our underwear and then I lost again and had to be the first one to get completely naked. It was very embarrassing and I tucked my cock between my thighs so none of the others could see it. I sat back down on the floor and felt very strange being utterly nude in front of my friends. And I started to get an erection. It was only a semi and I kept my hand over to hide it but my friend Gary saw what was happening and called me out. Said I had a boner and was excited to be naked with boys. And I kind of was but I'd never thought about boys before. Even though I'd had girlfriends already it was all very juvenile and I had never been naked with anyone at all, not only boys. So they all looked at my cock and I got really hard. And then Gary decided to take his underpants off as well. The game was forgotten. He had a boner too. And showed us. It was much bigger than mine. I was very excited to see it. The other two lads said we were being weird and got dressed. Gary reached out as if to touch my cock but I shied away and pulled on my clothes as well. So Gary did too. We all laughed it off and decided to go out and play hide and seek in the woods and nobody mentioned it again.
Then a couple of weeks later it was just me and Gary playing together and he said why not go to the woods for a game but all the various kinds of games we usually played only worked with more people so we were just walking around. Gary asked if I wanted to play cards again.... like last time.... and I knew what he meant and it excited me. We found a private spot away from any paths and out of sight and sat down. Actually, Gary didn’t have any cards with him so we just took it in turn to take off a piece of clothing. He watched me really closely when I was taking my clothes off and I watched him, but I was shy. Shyer of looking at him than actually being naked in front of him. eventually we were down to our jockeys again. I was getting hard and could see that he was too. He reached out and asked if he could take down my underpants so I stood up for him to make it easier. I was really hard and my cock popped out right in front of his face. He pulled my pants down. To this day, I can still feel his hands on my pants and against my thighs as they slid down my legs to my ankles. I stepped out of my jockeys and was naked. For the first time standing without hiding myself naked in private with another person. Gary said it was my turn and I had to take down his shorts. So he stood and I knelt and did the same to him. His cock was so big. And hard. And stood so upright like only a teenage cock can. He waved it in my face as I knelt there then squatted down opposite me and reached out. He took my cock in his hand and started to stroke it. I was so wet with precum my foreskin slipped easily back and forth over the head of my penis. Gary looked me in the eye as he stroked my cock and then said I should do the same for him. I reached out and touched his cock. It was so big. My hand barely went around it. And he wasn't quite so hard for the moment so I could feel the weight of it in my hand. It felt so great. The texture and the heft of it.... I remember it like it was yesterday. I started stroking him. Gripping firmly and sliding his foreskin back. His cockhead was glistening. There was zero friction. And so we were sitting facing each other with our legs across each other’s reaching out and wanking each other off. I was only wanking Gary for about 30 seconds and then he came. It was powerful and he shot his cum onto his hand as it gripped my penis and onto my cock and upper thighs which were spread wide. I felt his cum trickled down over my taint and into the crack of my ass. He kept stroking my cock. Gripping it harder and jerking faster and then I came too. My cum went into the air and onto my belly and then he aimed it towards himself and caught some on his cock and pubes. Then Gary leaned forward and laid himself on top of me. My legs were still apart and he lay between them. His cock was still hard after his cum and I could feel it rubbing against mine. He rubbed all the cum that was on his cock and pubes and on my belly together so he slipped easily over my body and he was humping my groin with his. I got hard again and reached up and put my hands on his shoulders. He kept humping and said to move my hands down so I slipped them down to the small of his back. Gary still said lower... to touch his ass... I was shy to do that, even after what we had just done... even while he was on top of me, humping his body against mine, humping his cock against my cock... even while my cum was lubricating everything that was happening. Gary reached behind himself with one hand and grabbed my hand and physically placed it on his ass. Told me to rub his ass and pull his ass towards me. And to use both hands. So I did and his humping got more intense and I could feel how hard his cock was as it rubbed against mine. And I was liking it and close to cumming again as I held the cheeks of his ass in each hand and pulled him onto me. Then Gary shuddered and came for the second time. I could feel his cock pulse and felt the cum squirt out between our stomachs and onto my body and onto my cock. He came for ages. Spurt after spurt. And that took me over the edge and I came again. Over my belly, onto his belly, onto his cock. We were a mess. And then, we were both almost ashamed. Pretended like it hadn't happened at all. Gary stood up and started dressing and so did I and we walked home. Said goodbye like we'd been doing nothing special. We never did it again. That was, to this date, the only sexual experience I have had with another male.
But it's fair to say it made an impression.