If Mari did nothing more than that, I would have been happy. Making out was fun, and I had no expectations of getting off. I always saved these encounters in my memory for later masturbation fodder, and assumed this afternoon would be no different.

I assumed wrong.

Mid-kiss, Mari suddenly pulled both her lips off my mouth and her hand off my dick. Sitting up, she quickly ripped her sweater over her head, baring her bra-clad boobs to my hungry gaze. Others had done the same sort of thing, and Sam had made cramming my face into her cleavage a personal fetish, but Mari took it a step further by unclasping her bra as well and tossing it aside. My eyes grew as wide as saucers at the sight of her big Double-Ds capped with crinkly brown nipples. She promptly cupped her right boob in her own hands, bent over, and fed the nipple right into my mouth.

I latched on like a starving infant, suckling away to my heart's content while grabbing all the tit flesh I could with both hands.

“Mmm... Matty..." Mari moaned, her eyelids fluttering while cradling my head to her bosom. She watched me nursing, a serene smile on her face.

A minute later, her fingers wrapped around my dick once again, and she jacked her hand up and down along its length with complete disregard for what might eventually happen if she kept it up.

Or perhaps she knew exactly what would happen. In fact, she seemed determined to make it happen. And whatever her motivations, Mari indeed made it happen. I was still suckling away at her beautiful breasts, having switched to the other nipple by now, when I felt the tell-tale tingling in my balls. I tried to fight the urge, tried to make this moment last a lifetime, but I couldn't hold it forever and she wasn't about to stop stroking. So I finally pulled my mouth off her teat and gasped, “Mari! Mari! Ohmigawd, Angel... You're gonna make me cum!"

If my intent was to make her stop stroking me, I failed miserably. Mari heard my words, moaned excitedly, and started jacking me even faster, rapidly spurring me on to the point of no return.

"Mari!" I pleaded again. "Mari... Oh... Angel... I... I...

UNNNGGGHHH! !"

My hands squeezed down on Mari's massive mammaries, my butt bucked up off Belle's bed, and my cock started squirting creamy cum all over my own belly.

“Ay, Dios mio!" Mari exclaimed at the sight of it. But she didn't stop stroking.

“Ungggh! Ungggh! Ungggh!"

Over and over I came, shooting at least six shots of sperm across my stomach. The remaining globs lost power and just sort of trickled out, but Mari kept pumping until there was nothing left. A lot of the white globules stuck to her skin, and on impulse she raised her hand to her nose to take a sniff. For a second there, I thought she was going to take a lick. But instead she stretched out her arm, holding her hand up for our audience to have a better look. "Can you believe I just did that?" she asked, elated with her own boldness.

Belle sat in her desk chair, an unreadable expression on her face.

“No," she replied in a quiet voice.

“I really can't."

Mari frowned at her best friend's flat tone. I was a little too wiped out (and blissfully happy from the orgasm) to really notice. But I noticed when Belle clenched her jaw, got out of the chair, and left the room.

Mari and I looked at each other, both of us unsure what to do. Mari spurred herself into action before me, sliding off the bed, grabbing a wad of tissues to blot up the spunk covering her hand, and marched out the door ignoring her toplessness. She must've gone to the bathroom to wash her hands, because she came back a minute Later, grabbed her bra and sweater, and gave me a quick peck on the lips.

"You know you're gonna have to get over this whole brother-sister thing, right?" she intoned seriously, more of a statement than a question.

I sighed, not sure how to answer her.

With a shrug, she got off the bed and started heading for the open doorway, intent on finding her best friend. But just before she went through, she paused and glanced back at me.

“Did you call me ‘Angel’ just before you came?"

I frowned and searched through my memory, not quite sure myself, but I thought I might have.

She giggled. "I kinda Liked it." And then she left.