My university room mate and I very soon became best buddies. Nothing sexual, just great buddies. He was a lot more conservative than me and, despite having a great body, shy to show himself around the room and in the communal bathrooms. He did, but always furtively. In fact he was quite a prude about all sexual issues and would slip away when discussion ever turned to erotic subjects as they invariably do amongst a bunch of horny university guys. He was also quite religious.
After about three months of rooming together I was woken one night by the obvious sounds of him wanking in his bed, which was about two meters away from mine. I was amazed - somehow I could not associate him with anything sexual. Out of pure curiosity and surprise I tried to cop a look but the room was quite dark so I could not see much. I must, however, admit that I did spring and instant boner.
But unfortunately I then did what ammounted to a very stupid thing. After he was done, I got out of my bed and walked quietly to the bathroom where I quickly jacked myself off. On the way back I collected some tissue paper and when I walked past his bed, I dropped it on his chest, maybe in an effort to tell him I knew what he did and that it was ok. Wrong. He did not say a word, neither did I. The next day he was obviously deeply embarrased and tried to avoid me as much as possible, and I was distressed for so stupidly encroaching into his privacy and compromising our friendship.
That night, lying in bed after we switched the lights out, I did the next stupid thing. In my stupid state of mind and with convoluted thinking, I thought that in order adress his discomfort, I would jack off and show him that it was ok, which I started doing. I was sure that he was still awake and convinced that he could hear what I was doing. AFter I was done I just lied quietly in the dark - no response from him. Somehow I expected him to say something but he did not. Now I started to feel real stupid, convinced that I had messed up in more ways than one, and it was my turn to feel deep embarrasment.
But then he suddenly got out of bed and left the room. After a few minutes he came back and, without saying a word, dropped a wad of tissue paper on my chest as he passed my bed in the dark.
Not a word was said about it then or thereafter.
The next day he was himself again and from there our friendship stepped up to a new level. Jacking off together at night became a normal ritual and while he remained discreet about his own nudity in the broader group, he became totally comfortable around me.
We both later moved on, got married and moved to different parts of the world. But we remained best of friends to the end, and when we saw each other once in a blue moon over the ensuing years, we always tried to find time and opportunity to rub one out together.
And yes, we both consider ourselves to be straight. We never had gender identity issues but loved each other.