For the longest time, Roy Mustang hated the rain. It wasn't just because these dreaded drops of precipitation rendered him basically useless. He mostly despised it because, when he would return to his apartment, on any rainy night, those cursed drops would seem to punctuate his loneliness. The worst rainy nights were the ones where insomnia gripped him. Those nights, he would have nothing better to do then listen to the rainfall on his roof.
That all changed one rainy March night when Riza Hawkeye went home with Roy. The visit's original intention had only been to pick up important paperwork that had a deadline of the next day. However, after Roy insisted that Riza stay and have a cup of tea with him, the two began talking. They talked for hours as the rain gently beat on the roof, adding a quiet soundtrack to their conversation. At around two o' clock the next morning, the two finally fell asleep on the couch, Riza's head on Roy's lap and Roy's hand entwined in her hair.
After that night, Riza never failed to visit each rainy night.
Only a few times did they ever cross the boundary. When they would step over that invisible yet omnipresent line, their titles disappeared and, if only for a moment, they were just Roy and Riza. They both knew the risk involved in crossing the boundary but, after the desire took their hearts captive, they found themselves not caring. They lived in the moment, something they usually didn't have the luxury of doing, and just enjoyed the feeling of rebellion.
Roy told himself that the reason he insisted that Riza stay that fateful night was because he didn't want her out in the rain. The real reason, though, was because he wanted someone to share those rainy nights with.