"Is my new librarian a Watcher?" she asks Sherlock the day after Mr. Giles joins the faculty.
Bella decides to see if she can obtain any value from whatever limited element of surprise she can get against Sherlock, and aims a kick at the back of his knees.
"Well done," he compliments, and counterattacks. Not at full speed. The point is to teach her, not to kill her.
Bella is going as fast as she can, and she needs to, to compensate for his skill and her lack thereof. Most of the aikido she watched involved working from someone attacking - she remembers this one throw - she tries it.
Half aikido and half making things up, she tries something else. The sooner she can convey her repertoire the sooner he'll know what else to teach her.
He still retains enough control that whenever she fails to block or dodge, he adjusts for minimal impact at the last moment.
Something else.
Something else.
She runs out of knowhow and starts improvising.
This way.
That way.
Little of this little of that.
"You're definitely a Slayer," he remarks—naturally, not out of breath. "Your instincts are good. Listen to them. But instinct can be improved upon."
"Yeah, how?" She's using her lungs differently than he is, but she's not tired - not yet.
And smoothly, seamlessly, he brings himself up to full speed and starts answering her every move before she makes it. Still with enough control to avoid hitting her full-strength. It seems almost choreographed, like they have been practicing this exact sequence for months and she just somehow forgot.
"If I can -" duck roll sweep-kick kip-up punch - "figure out -" feint uppercut grab throw - "what the instincts' moving parts are -" dodge block swat dodge - "would that help?"
"I can probably do that." (attack, attack, whoa duck dodge roll regroup jump kick) "Figuring out what's going on in my brain is a hobby of sorts for me."
(She is getting tired enough to notice, now, although not tired enough to slow her down.)
And what better way to help than to keep pushing those instincts into corners where their reactions are predictable to him?
"Well, usually," (duck spin swat) "it involves me sitting alone in a room" (sweep-kick block catch throw) "with a notebook, first" (ouch back up and punch) "but this'll be valuable material for it when we're through."
"Pleased to hear it," he says, evading a punch and then catching her hand to draw her forward and off balance. "It is also," stepping back out of the way of her counterattack, "quite a lot of fun."
"Yeah, I can see the appeal. I wonder if I'm going to be sore in the morning or if I'll just fix up overnight?" she says, still interrupted by the occasional wind-knocking-out or roll or that one time when she goes ahead and bites his sleeve but overall getting the hang of carrying on a conversation while in whirling violent motion. "I know I heal a lot faster but I don't know how it holds up against the kinda muscle tearing vigorous exercise causes."
"You'll be able to tell by whether I wince or not when you come by and it is time to do this again."
"I suppose I'll have more precision available. I am starting to get tired but I'm not actually sure if that's physical exhaustion or it being late. There's no clock in here. Hang on a sec while I get my phone?" she asks, executing a throw that, if allowed to land, ought to send him flying into a wall and give her the leisure to do that regardless of permission.
"By all means," he says, remaining where he is.
She consults her phone. "Not quite bedtime, but close enough that it's probably a good place to stop and head home," she says. "You escorting me?"