"What the hell are you doing?!" cried the voice of my sister-in-law. She was standing in the doorway of the bathroom I thought I had locked. She had just opened the door to find me, swim trunks down around my ankles, phone in one hand, cock in the other, scrolling through her Instagram and pumping myself furiously, respectively.

"I, I, I," I stammered, unsure of whether to try and shut the door, put down the phone, or pull up my shorts. My body decided for me, and I came all over the sink and my phone, with pictures of her clearly visible. As I caught my breath, I only saw her eyes, wide in shock, before the door slammed.

"Oh fuck, oh fuck, oh fuck," are all I could manage to say as my mind reeled. Is she going to tell my wife? Run screaming and tell everyone? I have such a good life right now, but my wife would kill me for this.

I managed to wipe everything clean, pull up my trunks, and quietly open the door in short order. I listen at the cracked door but do not hear my entire in-law family screaming in alarm, so I open the door wider and pop my head out. Clear to the left, and --

"I can't believe you were jerking off looking at my pictures," said a voice from the right. My sister-in-law--let's keep her anonymous and call her C.--was leaning against the wall in the hallway, arms crossed, which pushed her already ample cleavage together in her bikini top.

"Shhhh!" I hiss. I must have looked scared because she got a wicked grin.

"Don't worry. I won't tell L. what you were doing and what you were looking at."

I breathed a sigh of relief.

"That is, as long as you do what I say."

"What are--"

She stepped towards me and put a finger on my lips to shush me. With her other hand she grabbed my phone.

"I'll be back in a minute. Go back to the pool."

"Do I have--"

She pushed her finger harder against my lips before removing them and pointing outside. I hung my head and shuffled to the porch and pool area of the house my in-laws rented every late summer for a long weekend getaway for the whole family. So many good memories here, but now . . .

I found L. and sat down next to her. I grabbed a beer out of the cooler and offered her one, which she waved away. I couldn't concentrate and she had to keep repeating questions to me. In a few minutes she got up to jump in the pool with the various family members already playing volleyball. I admired her trim waist flaring to hips that I couldn't believe belonged to a mother of two.

"Eric!" My head swiveled hearing C.'s voice behind me. "You left your phone sitting upstairs," she said, walking with enough bounce in her step to send her breasts trembling with each step. I squinted my eyes shut and accepted my phone with a thanks.

She flounced down into the seat L. had just vacated. I tried to avoid looking anywhere in her direction.

She spoke quietly enough that no one else could here.

"If you want me to keep quiet, I have some rules for you. My sister is a nice person and I went through your phone. I'm glad you're not cheating on her, or at least you can hide it well enough."

"Of course not and I'll let you tell her before you make me do that."

"I'm going to make you do the opposite, actually."

"Wait, what?"

"I've put one of those porn accountability apps on your phone. It is linked to my phone and you can't remove it without me approving it. And I won't. I can see everything you look at on your phone now. So, from now on, you are only allowed to masturbate to pictures of L."

"Is that it? I can do that."

"Hasty, hasty. Only her and only when I say so. I'm going to give you windows of time when you're allowed to masturbate, but outside of that, you keep your hands off your cock. I mean you even hold it at the base to pee, understand?"

"Um okay."

"Now, I want some answers. If you hesitate, I'm telling L. Understand?"

"Yes."

"Do you think about L. when you jerk off?"

"Sometimes."

"What do you think about when you do?"

"I imagine her on top of me, no shirt on, fucking me."

"What parts of her body turn you on the most?"

"Hips and ass, face, breasts. Sorry, that's too stereotypical."

"No editorials. Just answer me. Now, name two favorite items of clothing you like to see her in."

"These bluish yoga pants and this clingy red t-shirt with no bra."

"You've been together a while. When you have usual sex, what do you do?"

"Um, well, usually we pull off each other's clothes--"

"Where are you?"

"In bed. We kiss and use our hands to start to touch each other. Before long I'm going down on her until she cums. Then we have sex. Usually missionary. God this is embarrassing and lame sounding when I say it out loud."

"What do you expect after 15 years? And what do you do when you're extra horny?"

"Oh, it depends. Then blowjobs are on the table, toys for her--I don't like telling you about her, since she didn't consent to this."

"Keep talking."

"Fine. Prostate massage, too. That's about it."

"Good." With that, she asked for a beer and stopped talking to me.

It was an uncomfortable day and night for me, as I slept restlessly. When I did sleep, C. was in her swimsuit, abusing me in different ways. I'd wake up hard and try not to touch it before falling back to sleep.

That morning, L. noticed my unease and I told her it was just my stomach feeling funny after the dinner, but that I'd be fine.

That afternoon C. caught me alone.

"Go to the bathroom. Open your photos and find your favorite picture of L. Then I want you to jerk off as soon as you find the picture. Then close the app right after you orgasm."

"These are weird rules."

"Are you refusing to do them?"

"No."

"Then hurry up. I've decided how long you have, and I'm going to tell you to stop when that time is up, whether you're done or not."

I was so horny after the last night's dream, I hurried up to the most remote bathroom and made sure the door was locked this time. I pulled out my phone and started scrolling through pictures of L. She was careful and wouldn't let me take any spicy pictures, so I settled for a picture of her in a dress she wore to a wedding. I remembered how she got more than tipsy that night. On the elevator up to our room, she was leaning back against me, pinning me to the wall with her ass against my hips. Grinding slowly, feeling me get hard against her. Trying to be subtle enough that the others on the elevator wouldn't notice. She fumbled with the door key as I slid my hand up the back of her dress between her thighs. She laughed and told me to hold on a sec, so I grabbed her ass beneath the fabric and said I was.

We were inside and didn't make it to the bed before I had her bent forward over the little desk table in the hotel room, her dress up over her hips, me kneeling behind her to pull her panties down, using my tongue to run up her slit, sliding in, back out, tracing her labia, running the tip over her clit as my tongue moved from place to place. I continued to rove, coming back to her clit more frequently, until she started pushing her hips back against me. I could tell from her breathing that she was getting close, so I dropped all pretense and kept steady pace and pressure on her clit until a long, drawn out "fuuuuuuuuuuuck" escaped her lips.

She was just recovering as I stood and slid myself in behind her. I began to pick up the pace and I saw her drop one hand to her clit, which I was usually happy to do for her, but sometimes she wanted it for herself. I could feel her start to tighten around my cock as another orgasm flowed through her body. As her breathing slowed, she looked over her shoulder. "Not yet?" she asked and I shook my head.

She dropped forward and my cock slipped out of her and she knelt before me. She jokingly said she was tired and just wanted me to finish, so she hoped I wouldn't mind if she had me cum in her mouth. She knew it was my favorite and before long I could feel the pressure building throughout my groin as my cock erupted down her throat.

My own cock twitched in my grip, spurting ropes of cum into the hand towel I had set down in front of me on the vanity. My hips continued to buck as I came. I was glad I had made it before C. stopped me. I closed the app, cleaned up and went back downstairs.

"Five minutes," she said as I came in the kitchen.

"Oh?"

"That's you're new benchmark. Next time, you have to cum quicker or you don't cum at all. Understand?"

"Um, okay, like later today?"

"Oh no, I'll tell you. Remember, no unauthorized touching."

She had to cut it off there, as family members started to trickle into the room to start to prep dinner.