Having a boyfriend, Remus decided, was nothing like having a girlfriend. Or at least, nothing like what he imagined having a girlfriend would be like, had he ever had one. Admittedly, his idea was based mostly upon the bragging of his mates and his observations of other couples. This relationship, though, was most definitely different. For one thing, there was a lot less handholding and fireside-cuddling and whispering, and a lot more arguing and pushing and insulting. Yes, a boyfriend was nothing like a girlfriend, particularly since Sirius was that boyfriend.
After all, Remus knew of very few couples that took years to get together. Unless, of course, one counted James and Lily. But considering that, despite James's best efforts, they weren't actually a couple yet, Remus wasn't inclined to include himself in that group. He didn't want to, anyway. He had long since come to the conclusion that James was utterly mad.
But their thrilling sexual tension had been anything but thrilling. For the most part, Remus and Sirius had been almost-completely-platonic-friends. Playful, maybe bordering on flirty, but definitely Just Friends. Except for the last year. Or two. That year had been plagued with inconvenient hard-ons and frustrating dreams and those half a dozen or so detentions from McGonagall for not paying attention in class. And, of course, Sirius's taunting and teasing and joking. Whoever thought that pining away for an unrequited love was enjoyable was even madder than James and Sirius combined.
The beginning of their relationship was a bit flat, compared to the films. The abandoned classroom on the fourth floor was not what Remus considered a romantic location. And rather than bold speeches to a crowded room, their "declarations of love" had been much more like blushing mumblings directed at shoelaces. This was followed by an awkward silence, and Sirius's casual "Shall we, ah, head on to lunch, then?"
Several confusion-filled days later, though, Remus realized that things really had changed immensely. Casual touches weren't very casual anymore, and he frequently found Sirius's arm wrapped carelessly around the back of his chair. And late nights spent cramming in the library were suddenly much more enjoyable. There was a lot more laughing and a lot less unrequited longing. And even though his schoolwork was taking a turn for the worse, Remus felt happier than he had in years.
Their first kiss was also rather anticlimactic. Following the full moon, Remus had been studying, exhaustedly, with Sirius's arm flung over his shoulders. Sirius had asked if he was okay, and when he wasn't satisfied with Remus's half-hearted answer, had lightly pressed his lips to Remus's. It was too short and too sloppy and their noses had collided uncomfortably. Remus thought it was perfect.
So yes, perhaps their relationship was understated and messy and awkward, but Remus concluded, so it should be. Perfectly imperfect.