Ashley returns before either of you have stripped

Ashley returns wearing a lab coat with small oval glasses sticking out of her breast pocket. You also see the outlines of markers in her larger lower pockets.

“I can’t work like this,” exclaims Ashley, putting on the glasses as she sees neither of you have stripped. As you both start to open your mouth she cuts you off with “and its Prof. Hoaka to you!” looking from above her glasses to both of you. “Now get my whiteboards ready!”

Tibby, still riding her mischief wave, looks at you with doe eyes and mutters “can you help me with that?“

You're always happy to help your pet out of her clothes, and you don't want to keep Ashley waiting. Approaching Tibby, you tug her shirt out of her pants and lift it up over her head. As it rises, she steps closer rubbing herself against you resulting in a grinning pet face in front of you when you pull her shirt over her head.

Dropping the shirt, you pull her in close and kiss her. But Ashley won't let you have any fun today. "Hey! Less kissing, more stripping!"

With a laugh, you relent and Tibby returns the favor by taking your shirt off. Under Ashley's impatient gaze, she has you step out of your pants and underwear as well before letting you do the same for her.

Ashley isn't satisfied until you're both naked, at which point she claps her hands and says, "Now then, let's start with a little quiz to see how much you already know. John, touch breast."

"Like this?" you ask, cupping one of Tibby's boobs and squeezing gently.

"Right. Now Tibby, can you tell me what the equivalent body part for males is?"

"Hmm..." Tibby thinks before declaring, "Man-boobs!"

"Hey!" you protest while Ashley laughs.

"No way. Our master has a manly man-chest, Tibby." Taking one of Tibby's hands, Ashley places it on your chest and moves it over your skin. "This is the pectoral muscle, see? Let's write it down."

Letting go of Tibby, she pulls out a black marker and writes 'chest' below your neck, then adds 'pecs' below that with an arrow to each side. "Now what males and females have in common are their nipples, the male version being less developed but serving the same function, if the right hormones were present."

"Wait, you mean dudes could make milk?" Tibby asks while Ashley writes 'nipple' on your chest and adds more arrows.

"That's right," Ashley says as she moves over. "With enough estradiol treatments people born male can develop functional breasts just like these," grabbing one of Tibby's boobs to write on it. "The genitals can't be changed without surgery however. You can't turn people into pets or stop them from being pets either. Because of the way estroxin interacts with the other estrogens, messing with it would have serious adverse effects."

"Oh, bummer," Tibby says. "I'd totally sneak John a pet pill so we can dress him up and cuddle and dote on him!"

You chuckle. "You'd have to take a not-pet pill or we'd never stop cuddling."

"And that's a bad thing?"

"Not for me, but it'd put all the weight of keeping us fed on Ashley," you laugh.

"And we can't have that, Mama Tibs," Ashley says with a smile. "Getting back to our lesson..."

Crouched in front of Tibby, she draws an outline of a reproductive system on her abdomen and marks all the parts. As she indicates the uterus she remarks, "the estroxin interaction is why you don't need birth control too, as it suppresses a critical stage of the womb's development that makes the uterine lining hospitable to egg cells. And why I had an IUD put in, by the time my estroxin levels rose that stage had already passed."

You and Tibby nod along, having learned some of this when they taught you about puberty in school. "Anyway," Ashley continues. "All these parts have their origin in the same structures as their male counterparts, even though they look so different. The gonads that become our ovaries, in boys shift down and turn into testicles."

She starts writing on your thigh and draws some more arrows. After marking all your parts she notes: "The penis is made of the same tissues as the clitoris too. They even share their method of engorgement, which means viagra works on women too. Maybe another experiment we can conduct?"

Your dick rises under her touch, as Ashley has been holding your length in her hands while talking. Tibby notices it and grins. "I don't think either of us need any help engorging right now!"