Who's at the door?

"Hey Aunt Olivia!" I heard my sister Christie say at the front door. I didn't know whether to feel relief or more panic. Christie knew about Aunt Olivia's lack of awareness, and she was my buddy, plus I was keeping more than one secret from Mom and Dad to protect her honor, but she was also family and could absolutely ruin us if she told people what she'd walked in on. But more importantly, why was she at our door in the first place? We were supposed to have some modicum of privacy here, in our condo in a secure building.

Momentarily incensed at the intrusion, I yelled at her, "What the hell are you doing here Christie!? How did you even get up here?"

"I followed some college chicks in," she said. So much for the high-security building. "Hey, why are you guys naked?" Christie asked with a goofy grin.

I stammered, used to coming up for explanations that would satisfy Aunt Olivia, which meant I could say the first thing that popped into my head and as long as it was in English, she'd smile and accept it. Coming up with a solution that would satisfy my ball-breaking sister was proving much more difficult.

"We were showering separately after our workout session and were alarmed to hear someone at the door, since guests usually use the buzzer system, and I ran out to see who it was. You know how oblivious I am, I forgot I was naked, and Mark realized this and came out to make sure I was okay."

Those words came out of Aunt Oblivia's mouth. It wasn't surprising on a certain level, since behind her obliviousness she was very intelligent and well-spoken, but that level of self-awareness was not something she'd exhibited much in our antics over the past few months. She must have realized the urgency of the situation and summoned all her mental power to save our butts.

"Oh okay," Christie said with a grin. I doubted that she really believed it, but she didn't run off in horror, and instead pointed to her suitcase. "Come lug this in Mark! I'm pooped!"

Christie is only about ten months younger than me (Mom and Dad must have had a lot of passion early in their marriage) so we never quite had the bossy big brother and bratty little sister relationship. We were more like twins, peers, and went through life together back on the farm. We had the same group of friends and we got along well enough, even if we bickered and teased each other plenty. Actually she broke my balls like one of my male buddies... it's not for everybody, but I liked it.

Glad that we had averted the crisis for now, I ran to the hallway and pulled in her rolling luggage and closed the door behind us. "Hey why are you even here?" I said, finally thinking to ask.

"Uh, remember we planned this when you came back last month? I said I was coming for a campus visit," she said.

"Well yeah," I said, vaguely recalling that, "But like... today?"

"Check your phone, genius."

I grabbed it off the kitchen counter and she had been texting me all day. Work and, less justifiably, banging my aunt, had meant I hadn't really been checking my phone.

"And I told Aunt Olivia," my sister said, "She's the one who actually owns the house."

"Oh yes, I knew she was coming today," Aunt Olivia said smilingly. Well, she sure got back to her usual level of awareness in a hurry.

"Anyway I'll be here for the weekend," Christie said, "My tour is tomorrow but I wanted to get to experience the social part of college. That's the actual important part to figure out to see if the school's right for me."

That made sense, I suppose. Christie was a little more academic than I had been, but she was very social and in no hurry to start a 9-to-5 job. Why not find herself at college for four years? But couldn't she pick another college? I kinda had a thing going on here.

"So are you staying for dinner, or off to bar hop?" Aunt Olivia asked.

"Oh I'm just 18, I can't drink yet," Christie said, "I'd love to have dinner with you guys". She's such a good girl around family... of course I knew being 18 had hardly stopped her from getting plastered at her birthday party.

I breathed a sigh of relief though. Christie didn't seem to notice we'd just been having sex. I looked at Aunt Olivia's body, to me she looked aroused still, but at least there was no signs of my cum on her thighs. She must have cleaned it discreetly. It seemed like we were in the clear for now.

"Sooo should I get naked too for dinner?" Christie said impishly.

Oh shit, we were still naked. I was totally nude in front of my little sister. I awkwardly covered myself up with my hands and blushed.

"Just now noticing huh?" Christie teased, "Ain't nothing I haven't seen before."

We did have a casual attitude about nudity around the house, but still. "I'll be right back. Get dressed too, Aunt Olivia."

She walked nonchalantly to her room and I went to mine. Well this was going badly, but Christie had shown up with no real warning. What could I do?

It was Aunt Olivia's turn to make dinner, so she cooked a stir fry. Christie had settled in and joined us. She's tall for a girl, at 5'6", with straight brown hair to her shoulders in a clean style, almost the female equivalent of a "bowl" haircut, and straight bangs in front. She plays soccer and is athletic but in a stout way, without being fat at all, she's just not skinny or super-toned like Aunt Olivia. She has broad shoulders and wide hips, and to be honest, big boobs.

"Can I have the sauce, Mark?" Aunt Olivia asked me casually as we ate.

Damn, she wanted me to cum on her food. She still thought that was just a sauce I added. I found myself oddly wanting to have her jerk me off with my sister watching. It would be so hot to show what I could Aunt Olivia to do in her infinite obliviousness. But I couldn't really do that.

"Uh, we're out," I said awkwardly. Olivia frowned and my sister looked at me curiously. We finished dinner and Christie helped with the dishes, then we all watched a movie before bed. It was wholesome family fun.

We said goodnight. The plan was for Christie to sleep on the couch but she would use my bathroom to get ready for bed. This was nothing new as we'd shared a bathroom back home for the previous 18 years. Real farmhouses don't exactly have en suite bathrooms for each bedroom.

She walked into my bathroom in just her bra and panties, but that too was nothing new for me. I was in my boxers and finishing up brushing my teeth.

"So," she said, "You're doing it with Aunt Olivia?"

I spat out the toothpaste. "What!?" I asked nervously.

"Oh come on, you answered the door naked and there was cum dripping down her leg," my sister said, "She's the oblivious one, not me, remember?"

I looked down. It was pretty obvious what had been going on, I suppose it had just been wishful thinking to hope that Christie hadn't noticed.

"Relax," she said, "I mean I think you're a pervert but probably most guys would bang their hot aunt if they could. Men are such horndogs. I won't tell Mom and Dad... if you answer my questions. How'd you talk her into it?"

I sighed. Christie knew me too well, if I lied she'd sniff it out easily. "I just... um... you know how she doesn't notice anything, and will believe whatever you tell her..."

Christie raised an eyebrow. "You tricked her into having sex with you?"

"That's a mean word for it. Her body knows what we're doing... and I think her mind does on some level. She just doesn't really put two and together and realize we're having sex. She's never said no."

"Damn, Mark," my sister said with a giggle, "I can't believe you did it. I always wondered if someone could pull that over on Aunt Oblivia."

I was surprised by that reaction, but then again my sister was a bit of a prankster and she was also very interested in sex.

"I know I shouldn't have, but she likes it... and she's lonely," I said, recalling that night in bed when she'd lamented not having anyone to sleep with.

"Well, if I told anybody, you'd be in deep shit. You know that right?"

"Yeah," I said, looking at my feet.

"I won't tell anyone, if you do just one thing," she said with a wicked grin.

What did she want? Money? My truck? I had no idea, but I had to agree to it. "Fine, what?" I asked. She took her time, though, finishing up washing her face then looking at me through the big mirror in front of us.

Her grin became downright wicked. She opened her mouth and said, "Let me join in on your fun."