Summary: Marceline is really, really bad at the relationship thing. So Bubblegum decides to step up.
One night, in the castle garden, Princess Bubblegum grabs Marceline and kisses her. Marceline reacts by not reacting at all, and after a few minutes Bubblegum sighs and says, "I'll see you later, Marceline," as she walks off. Marceline eventually stops floating insensibly long enough to get back to her cave, find a large rock, and smash her head into it hard enough that she's left with three smallish rocks, and a headache that takes two days to fade.
Glob, why is she so bad at this?
When Bubblegum knocks on her door days later, she's carrying a large bag, and Marceline seriously considers not letting her in. Except that Bubblegum was looking right at her when she pulls back the curtain, and she's already made things awkward enough, so...yeah. She opens the door.
"What's up, Bonni?" she asks, and belatedly realizes she's standing in the doorway, and pretty much blocking Bubblegum's entrace.
"I thought maybe we could hang out for a while," she says with an admirably friendly smile, considering what Marceline...considering. "If you're not busy."
Of course she isn't busy, and of course Bubblegum can come in...except she can't, because Marceline's feet are still planted like she's preparing to be tackled by a rhino, or something. She forces herself to move, and says, "Do you wanna...?"
Bubblegum generously slips past without making Marceline finish that thought, and perches on the edge of the coffee table. One day Marceline's going to ask why she never uses the couch, but first Bubblegum pulls two books out of the bag. One doesn't have words on the cover so much as just a jumble of letter and numbers next to a bunch of geometric shapes, but the other...
Marceline darts forward and grabs "Classical Masterpieces for Electric Bass" out of Bubblegum's hand. "Score!" she crows, because while she's freakin' boss at the bass, everyone can appreciate the masters.
"Do you have any of that juice you had last time?" Bubblegum asks, now pulling a cushion, of all things, out of her bag.
"Oh, yeah--here, let me grab you some," Marceline says, because she's finally remembered that she's the host. But first she darts into her bedroom to grab her axe, because, well, priorities.
The next hour or so is really pleasant, yeah, but also easy in a way Marceline wasn't really expecting, given, you know, that whole garden thing. The bass's music is constant, as always, but Bubblegum remains quiet unless she's murmuring math formulas out loud as she tries to solve them, and Marceline only occasionally calls out, "Hey, listen to this."
Bubblegum sets down her book right around the same time Marceline finishes up "Dance of the Sugar Plum Fairy," which just seemed kind of appropriate. Bubblegum is looking at her expectantly now, so she forces herself to stop strumming, although her fingers still dance across the strings nervously.
"Are you upset I kissed you?" she says, and Marceline's finger plucks in reflex. The E that rings out is so sharp and loud they both wince, a little.
"...No," she said, because it's true. She's pissed, but only at herself, because she was such a spazz that night, and she's doubly pissed at herself now, because it's all she been thinking about, but she still doesn't want to be having this conversation. She shifts her left hand and thumbs the D string, but doesn't strum.
"Was it bad?" Bubblegum asks before Marceline can think of anything else to say, because the only thing that comes to mind is, Why did you do it? and there's no way that doesn't sound pathetic.
"No!" she says, sharply this time, because geez. That was not the problem.
Bubblegum looks surprised, and maybe...pleased? "Well, would you like to do it again sometime?"
Marceline doesn't know what her face looks like--although it feels like it's on fire, which is just awesome--but whatever it is Bubblegum sees makes her clear her throat and say, "Not now, necessarily, but maybe..."
"Yeah," Marceline says, and sounds a little hoarse herself. "Um, can I get back to you on that?" That answer is of course an unequivocal YES!! and that is the problem. Marceline's never had a relationship that didn't crash and burn, and those weren't with super genius princesses who looked like, well, that. Sure, she'd thought about it, and apparently Bubblegum had too, which means...well, she doesn't really know what it means, and maybe that and other things make her a little gunshy. She runs her fingernail over the familiar ridges of the strings.
Bubblegum sighs again, then grabs the bottom of her shirt and shucks it off.
Marceline doesn't actually remember the dash to her bedroom closet, or when exactly she turned into a bat, but here she is. Bubblegum's still in the living room, laughing so hard it sounds like she might start choking.
"Marceline!" she cries, eventually, around stuttering gasps for air. "I was hot--it's a sweater!" Which--oh. In retrospect, it had looked pretty fuzzy for a shirt. Marceline doesn't answer, but does beat her head against a shoe box a few times.
"I knew that!" she yells. "I was looking for...stuff."
"Never mind." There is no believable way to finish that sentence. Instead she knocks her head one more time, shifts back, and slips out of the closet as quietly as she can.
When she gets back to the living room, one look at Bubblegum tells her that no excuse is going to fly. "What did you think I was going to do?" Bubblegum asks, a laugh in her voice. As if she doesn't know--oh, plop, she probably knows exactly what Marceline thought she was going to do. Oh, gumballs.
Marceline is going to die. She is going to crawl in a hole, and die of embarrassment.
"Honestly," Bubblegum says casually, like Marceline isn't literally dying in front of her. "As if I'd let you get under my shirt on the second date."
"The second--what? What?" Marceline demands. Bubblegum's laughing too hard to answer. "What was our first date? It wasn't--tell me it wasn't the garden. What the plum, Bonni, our first date cannot be me floating around your garden like a braindead zombie! I mean, geez, let me do better than that!"
Bubblegum's quieted down again, and Marceline mentally reviews what she said and...oh. Yeah. She kind of talked herself into a corner there. But Bubblegum's eyes are shining, and she's smiling like she's really happy, here, and...Marceline doesn't take it back.
"Do you think you can?" she asks, gently. "Do better?"
Marceline darts forward. She stops, though, inches away, because... "I'm not very good at this."
Bubblegum threads her hands through Marceline's hair, and tugs her those last few inches. She still starts them, but Marceline follows her lead, this time.
"Liar," she breathes when they pull away. Marceline has to get her brain back online to figure out what she's talking about, but oh. She almost protests, because she hadn't meant bad at kissing, she had meant, Don't let me screw this up like I always do. Then Bubblegum pulls her in again, and, well.
She always has been good at improvising.