A/N: Yachiru is intended to be a bit older (about the same age as Hitsu in the present manga), just so that's clear. I'm posting this as Hitsu and Matsu (characters) but I will change if anyone recommends.
Please enjoy, and if you feel a little more perverted when you leave, then my work is done. Lol, j/k.
Really, he didn't know why he let Matsumoto talk him in to going with her to deliver papers, but, they were headed back to the Tenth, passing the Sixth Division office when a strange noise gave them pause. Matsumoto's eyes went big and round, fearing the worst. Her fears were confirmed when she heard the first voice speak.
"Ow! Byakushi, it hurts!" the voice of Yachiru cried, sounding near tears. Matsumoto looked to Hitsugaya, hoping what she was thinking was wrong. Unfortunately, Hitsugaya seemed to be thinking the same.
"It's going to hurt the first couple of times for you, but you'll get used to it soon enough," Byakuya's voice replied. It definitely sounded like he was panting. Hitsugaya's face went scarlet and Matsumoto's matched.
"If it wasn't so big…" Yachiru sobbed.
"It would still hurt some. It would have to be incredibly tiny for you not to hurt at all," Byakuya replied.
Matsumoto's eyes were squinted as she mumbled "And they call me a pedophile…" She caught the questioning look on Hitsugaya's face and quickly added, "Nothing, Taicho!"
"Quit pushing so hard!" Yachiru cried again.
"Nothing will happen if I don't push hard, Yachiru-chan." Matsumoto just knew, then and there, that Byakuya was taking advantage of poor little Yachiru. Why else would he call her Yachiru-chan?
Matsumoto whispered to Hitsugaya, "Taicho, we should tell someone."
Hitsugaya motioned for Matsumoto to be quiet, and pressed his ear to the door. Matsumoto mumbled "Pervert!" under her breath, but Hitsugaya paid no mind.
"Byakushi, can't we try this some other time? It really hurts," Yachiru whined.
"I have told you, Yachiru-chan, it will hurt then, too. At least if we do this now it will not hurt so next time," Byakuya declared. Matsumoto nearly fainted.
"But, Byakushi, how come you're havin' all the fun? You said this would be fun for me, too!" Yachiru was outright crying now.
"Who said I was having fun?" Byakuya responded.
Matsumoto muttered to Hitsugaya. "Well, at least he's not being a pig about it." Hitsugaya just looked quizzically to her. "You know what I mean!" she huffed.
"You are, cause you're smiling. And you never smile!" Yachiru accused. Matsumoto didn't faint, but she did go weak in the knees and fall to the ground with a loud thud.
Hitsugaya rushed to catch her, and at least managed to keep her from hitting her head or anything.
"Did you hear that Byakushi?" Yachiru asked, voice no longer tearful.
"Probably just someone blowing something up in my division compound again. Actually, I imagine it is Abarai." Hitsugaya heaved a sigh of relief. But, maybe Matsumoto was right, and they should tell somebody. But who would they even tell?
"Ooh, I wanna see! Let's go see what happened, Byakushi!" Yachiru seemed to be excited again, though still short of breath.
"Yachiru, it is very important that we finish what we're doing first." Hitsugaya and Matsumoto shared a confused look.
"Fine. I know, why don't I do it that other way you talked about? That way it doesn't hurt anymore," Yachiru suggested.
"I suppose that is a permissible alternative."
"I just put my hands like this, right?"
"Correct," Byakuya confirmed. A sharp intake of breath was heard. "Not quite so tight, Yachiru-chan."
"Sorry," Yachiru mumbled, not sounding sorry at all. "I move 'em like this, right?"
A few seconds of near silence passed, in which Matsumoto assumed Byakuya nodded to Yachiru, and must have been enjoying himself. On the slightly less bleak side, Yachiru seemed to be panting in pleasure as well. As horrible as it seemed from the outside, both seemed equally happy with the situation.
"Taicho," Matsumoto looked up to Hitsugaya from her sitting position. Hitsugaya looked down to the woman still barely supported in his arms. "Shouldn't we tell Zaraki taicho? I mean, sure, she's grown up some, but…"
"And have Kuchiki taicho after us? Or both of them if we're wrong?" Hitsugaya looked frightened.
"But, Taicho! What if they're doing what it-" Hitsugaya clamped a hand over Matsumoto's mouth. Which immediately resulted in her licking and sucking on his fingers.
"We'll wait to see what else we can tell. They're probably moving furniture or something. Dammit, woman, stop that!" Hitsugaya fussed. Matsumoto continued suckling Hitsugaya's fingers. If he was going to put his hand over her mouth to try to get her to shut up, he was going to pay for it.
If he really wanted her to shut up he'd put his mouth there instead.
"Yachiru…" Byakuya voiced. Matsumoto ceased her aggravation of Hitsugaya long enough to determine the voice was husky and deep. It definitely sounded like they were "in the middle of things."
"Mmm…" Yachiru hummed. A beat later they heard, "Is it supposed to do that, Byakushi?" her voice, too, was husky and panting.
"That is the idea, yes," Byakuya managed.
"Uh-oh, I spilled it," Yachiru sounded scared that she'd done something wrong.
Was that a chuckle from Byakuya? Matsumoto finally gave in and fainted. Hitsugaya groaned as he repositioned her against his frame. She might not be too heavy, but he was still shorter than her.
"That's okay, Yachiru-chan, we can just wipe it up for now."
Hitsugaya quickly revived Matsumoto, and they pounded on the door a few seconds later. Without waiting for an answer, Hitsugaya burst inside. "Kuchiki taicho, I must ask what you are doing in here, with Kusajishi no less," Hitsugaya demanded. Just because both were clothed certainly did not mean anything.
Byakuya raised one fine eyebrow, casting Hitsugaya and Matsumoto a strange look. "I have been teaching Kusa-" Yachiru tugged on Byakuya's sleeve, "Yachiru-chan to fight using only her reiatsu. As you can clearly see, Hitsugaya taicho, we have been forced to move the furniture of my office and somehow in the process spilled my tea."
"Oh, erm… that's all we were wondering. Thank you for allowing us to survey you on such short notice!" Matsumoto finally managed to find a decent excuse and she and Hitsugaya were out of Byakuya's office in split seconds.
"I am never delivering paperwork to the Sixth Division again," Matsumoto declared as they reached the safety of their own office. "I'll just make Renji come and pick it up from now on."
"That's perfectly fine with me," agreed Hitsugaya.
"You know, Byakushi, some day we're going to get caught. Then what are you going to do when Ken-chan finds out?"
Byakuya gave something of a shrug. "I believe I can handle your 'Ken-chan,' Yachiru," Byakuya smiled as he leant in for another kiss.