It was during their sixth year when Hermione and Percy began corresponding. She had always had a crush on him and despite his problems with the Weasley's she felt he had a lot of potential. Their letters started out light and fluffy. Percy advised her on school work and she told him light hearted stories intended to make him laugh. Slowly but surely the letters became more intense and Hermione comforted a lonely and frightened Percy Weasley.
When he was ready to make amends with his family she went with him, holding his hand as he apologized for what he had done. It took Fred and George a little while but the rest of Percy's family welcomed him back with open arms and Percy felt it was due to Hermione. The two slowly became the best of friends and when the war was over, the each helped each other grieve; Percy for Penelope and Hermione for Viktor Krum.
Years passed, at 25 years old Hermione had felt certain the crush she had on Percy had completely disappeared. Her longest relationship to date had been Ron, who ended their 3 year long relationship for Cho Chang. But Hermione didn't get bitter, she chose to be happy for Ron and remain as close as they could.
The night of Fred and Angelina's wedding both Hermione and Percy got completely pissed. Waking up with the next morning was awkward but they decided it was just a night of physical comfort. They were both lonely and over worked and needed someone. They stayed friends and never told anyone what was going on between them.
Four months later and several drunken nights of physical comfort, Hermione admitted to herself that she was falling for him. Percy made it clear that he didn't want any kind of attachment, so Hermione kept her feelings to herself.
It wasn't until their fling threatened Hermione's well being that she cut it off. Percy's told her he understood but he looked disappointed. Hermione remained strong and didn't let it affect her, at least not that anyone could see.
She saw Percy occasionally at Weasley functions and to the untrained eye no one could see what lay beneath. No one, not even Percy, could see her longing or her pain.
Hermione cried at her desk later at work, trying not to remember the way he smelled, or the way his brown eyes would dance as he laughed. Yes, despite herself, she had fallen for Percy Weasley. But she couldn't risk it. Being in love with him could cause irrevocable damage and she couldn't risk it.