This sounds very painful for you. You say you just want friendship but I think deep down you would be hoping for more, and this would cause you even more pain if you try to pursue it. Some friendships are doomed to end, and you must accept that, for the sake of your own peace of mind. Don't let this become obsessive for you. You need to tell yourself that you deserve better than living on the margins of someone else's life. There will be other people who will want your friendship, in a way that this man does not. Seek out those other people, try not to compare them unfavourably with this man, and gradually they will replace this man in your thoughts. Good luck for the future.