Sole friendship without any sensual interplay or romantic feelings? To a certain degree. I believe that when a man and woman get really close as friends, and I mean extreme besties close, sooner or later, person 1 ends up falling for person 2. It could take days or it could take years but it eventually happens and person 1 usually decides to keep it from person 2 for the sake of maintaining the friendship and to prevent putting person 2 on the spot and in a difficult situation. This may not apply all of the time but I personally think it does happen a lot.