Well, you were feeling a bit thirsty. So, you clambered along through Rouge's cleavage, and ducked underneath the heart-shaped breastplate to sidle along her breasts, soon coming across her nipple—which was larger than you were! You gently pressed a hand into the areola, and that elicited an immediate reaction from the bat—a delighted chuckle. "Hmm, admiring my tits up close, are you?"
"Y-yeah..." You cling to the nipple flesh, glancing around and finally noticing something missing. "Huh, you... don't wear a bra?"
"Nope. I tried wearing some, but the straps always felt awful against the base of my wings." You were about to counter with something you remember her wearing in some of the spin-off titles, before she added "I do have a sports bra, though. Had to be custom-made to an extent, and it doesn't play well with my jumpsuit, but it does the job when I'm not out treasure hunting."
"Wow..." You find yourself blushing at that. "I-I... wouldn't mind seeing you wear that..."
"Hee hee, you just might, cutie. Now then, could you perhaps provide a bit more rubbing down there? That first bit of yours felt really nice."
Flustered by her request, you immediately accepted it, bringing your tiny hands up and down along the nipple. With every other press, you got a coo of delight from Rouge, and occasionally she did another graceful spin in the air (which made you have to grip tight out of an ultimately unwarranted fear of flying out, which only fueled the cycle further). Eventually, your masseuse work bore fruit—or rather, milk—and you scrambled over to the duct to lap up the white liquid spoils. And the result was more than worth the effort. "Mmm... so sweet..."
"Partaking in my milk, hm? Glad you like it. ...Y'know, you're probably small enough that you can climb in there and drink your fill. Just so long as you watch out for the gems in there."
"Whuh—?!" That statement dumbfounded you enough that you almost let go of your tit perch. "Y-you... y-you put...?"
This time, Rouge had a boisterous laugh for you. "When I said they're the best place to stuff a gem, I didn't just mean between them! Though it's tough to get them back out, I'll admit, the sensation of having my boobs filled like that... it really just can't be beat."
"Huh, so they're sort of your own... treasure chest."
That terrible joke was enough to earn laughter from the both of you, Rouge's lasting a delightfully long time. "Hah... yeah, I suppose it is. Feel free to climb in and admire them—you're probably too tiny to push them out, anyways."
"Y-yeah, probably." The thought of stealing gems from her tits enticed you... but you were minuscule, and she was a master thief for a reason. Would probably be best just to look, and drink up all the milk you want... Or, if you're already feeling stuffed from the small amount you drank, there's plenty more miles of bat body to venture across.