If you were to ask Ruby about the moments leading up to her first kiss, she wouldn't have been able to tell you. Weiss knew this because she'd heard the younger girl say so herself when Yang had accosted her, shortly after realizing that Ruby and Weiss had moved passed the "just friends and partners" stage and into the "cuddling and occasionally kissing" stage. Weiss supposed that would make them girlfriends, but neither of the two had used the term yet.
Back to Ruby, though. Weiss had rolled her eyes when Ruby had confessed that she "was too caught up in the moment to remember the details". An incredibly Ruby-like thing to say, really. Weiss, however, remembered all the details. Not that she'd been any less caught up in the moment.
It had started innocently enough, with Weiss attempting to help Ruby cram for an exam in Oobleck's history of Remnant class. It had started out as Ruby and Yang, but Yang had resigned herself to a failing grade rather quickly and left the partners to study by themselves. Ruby had similarly wanted to give in shortly after, but a withering glare from Weiss had shut that idea down fast. The studying did turn out to be helpful in the end. Ruby managed a middling B, and was prouder of her grade than Weiss could ever be of anything even close to that low. How she managed to pass at all after she had been so distracted from her studies was a mystery.
And who was to blame for the distraction? Well, Weiss had to admit it was her fault, to an extent. As much as she had hated herself for it in the moment, Weiss looked back on their first kiss with a fond kind of embarrassment. She had gotten so frustrated with Ruby's lack of attentiveness that she promised her partner a reward if she were to ace the next small quiz Weiss was preparing. Naturally, unable to stand the mystery, Ruby dove into her studies, all distractions completely forgotten. Weiss, unfortunately, hadn't actually expected Ruby to ace her little quiz. It was, in no uncertain terms, completely unfair, covering topics that they hadn't even touched on in class. It was designed to make Ruby fail at least a few of the questions, all so Weiss didn't actually have to think up some mystery prize.
Of course, Ruby had gone and breezed through Weiss's test, answering every question with ease and then demanding that Weiss make good on her promise of a reward. She had looked up at Weiss with those damn pouty eyes, and, without thinking about it, Weiss found herself pressed up against Ruby, her lips placed on her partner's.
"How's that for a reward?" Weiss had said smugly, proud of herself for winning another battle of wits with the younger girl for the slightest fraction of a second before she fully realized what she'd done. Only when she caught sight of Ruby's face, her mouth hanging open like a dead fish, did the situation sink in.
Weiss had, admittedly, screamed a little bit. Whether it was from the shock of realizing what she'd done or in excitement from her sudden courage to act on the feelings that had been growing all semester, she couldn't say. She turned to dash away, to distance herself from the moment as much as possible until her head stopped spinning, but Ruby had grabbed the sleeve of her jacket and held fast.
Before Weiss knew what was happening, Ruby had kissed her again. Or rather, Ruby had kissed her the first time, since Weiss had been the one doing the kissing before. Ruby just sat there, slightly stunned. This time, however, they were both fully aware of what was going on. The situation was absurd and honestly didn't make much sense, but neither of them really seemed to care. All Weiss knew was that when she pulled away, all she could think about was kissing Ruby again.