A/N: We're just going to pretend that Mac doesn't like-like Lisa here, because, while I don't ship it, I think it would be pretty rude of Lisa and Leo to completely disregard Mac's feelings.
For this to make sense with the episode, imagine that Mac knew that it was Leo wearing Lorenzo's mask when the inventor tried to trick him, and so, what he said was actually a ploy to get the two together. To plant the idea that Lisa liked him in his head. And you can also imagine that Mac's distain whenever Lisa moons over Leo is because he's exhausted with the pair of them dancing around each other.
After Mac had fully left the workshop, Lisa turned back towards Leo. She took a second to build enough nerve to bring up the topic that had been on her mind since it was brought up earlier that day.
"Leo, you know what you asked me at the ball?" the girl asked, looking down at the table, unable to meet the young inventor's eyes.
"Uh, no, what?" Leo asks, a smile flitting across his face for a brief second, before he purposely schooled his expression into one of confusion.
Lisa had glanced up at the boy when she heard him speak, and she caught the smile on his face. She gave him a deadpan expression, but it was laced with amusement.
"Oh!" Leonardo laughed, rolling his eyes at himself for getting caught. "You mean when I asked you if you liked me?"
"Um, yes. That." The girl avoided the young inventor's eyes once again, fiddling with her cup on the table. "Mac might have been right. About me… my feelings. Uh, for you."
The boy grinned. "That's a relief."
At this, Lisa looked genuinely confused. "And why is that?"
"Because, while you were missing earlier, I realised that I have feelings for you too."
"And how did you work that out?" She asked, curious as to what might've happened that could have led him to that conclusion.
"Well, I realised I was much more worried about you than I was about Lorenzo, which seems illogical, because I know you can hold your own much better than he can." Leo looked down at the table, suddenly shy. "And when we hugged when you found us, I didn't want to let go. That's why I kept hold of your hand when Mac pointed out Lorenzo's voice."
Lisa's face grew fonder and fonder as the boy explained himself. "I didn't want to let go, either." She admitted, smiling.
The bells chimed in the distance, indicating Curfew had arrived. Lisa and Leo both knew that, while Maestro Verrocchio, Cosimo and the other apprentices were fast asleep after their day at the carnival, Lisa needed to change back into Tom, in case anyone woke up and entered the workshop area.
"I need to change." The girl stated unnecessarily, a frown marring her face. "It took so long to get this dress on." She muttered to herself.
Unsure, Leo asked "would you like some help?" and, before he realised what he was doing, he was standing in front of her, holding out a hand to help her to her feet.
Lisa took the offered hand with a smile, and didn't let go. "If you wouldn't mind, Leo. Grazie."
The pair were toe-to-toe, though the girl had to crane her neck to meet the eyes of the boy. While she had enough nerve, Lisa rose to her tiptoes and pecked the young inventor's lips. When she dropped back onto her heels, Leo was in such a daze that she had to drag him by the hand she was still holding out to the gated outside area of the workshop.
It took a while for Lisa to finish getting changed, because Leo decided to pay her back for the surprising kiss, teasing her into giving him more kisses, and he did this by taking his time undoing each hook on the dress. When it was time for the girl to put her wig back on, the boy took the last part of her disguise into his own hands, setting it onto the workbench beside him.
Leonardo ran both his hands through the curls, then cupped them around Lisa's cheeks. At her grin, the young inventor dove in for a passionate kiss, fingers slipping from her face, threading through the curls once again. Lisa's hands grasped the collar of the boy's top, pulling him infinitely closer.
After more time than was strictly decent for a non-married pair, they pulled away from each other, panting heavily, huge smiles gracing both their faces. Leo helped Lisa put her wig on, delicately tucking the curls in.
Leo then took Tomaso's hand, leading the way up to the room that was theirs, settling into their own beds, whispering a 'goodnight' to each other, before falling asleep.
When Mac snuck in the next morning, he was greeted to the sight of his friend's fingers brushing each other's in the space between their beds.
Shaking his head with a smile, the boy walked back down to the workshop, letting the pair sleep for a while longer.
