Anna.

As Billy woke up, he looked at the silhouette of the woman who was currently slinking into his room. At first, it could have been either Heather or Anna, but as she got closer he recognized Anna's figure.

Before he had time to say anything, Anna hopped up onto his bed and straddled him. She was wearing just a tank top and a pair of revealing pink panties.

As he felt Anna straddle his hips, Billy sensed how **** his position was and started to struggle. He needed to get his arms out from under the covers in case he needed to be able to defend his face. But he was sleepy, and Anna was fast, and she quickly found his left arm under the sheets and used her leg and knee to pin his arm down to his side under the covers. His right hand, he managed to get out, but Anna seized his wrist and pinned it to the bed near his head.

Billy struggled to free either of his hands, panting. Anna was sitting right on his hips, his rapidly hardening cock able to feel her soft yet firm ass.

"What's the matter, bro? Afraid I'm gonna beat you up?" Anna giggled. She faked a punch with her right hand, and Billy flinched. He also couldn't help glancing at her tits bouncing under her tank top as she swung her fist. And he could tell by her smile that she noticed.

"I won't...as long as you answer my question from the other day," she said. Billy was confused. The other day? Anna must have noticed his confused face.

"Let's see...you came home all bruised up and so weak that I pinned you up against the wall with one hand...and I wanted to know whether you got beat up by another woman?" Anna said.

So much had happened in the past few days that it took Billy a second, but he remembered. It was after Karen had knocked him out. He really, really, did not want Anna to know that Karen had knocked him out. He didn't have a lot of good options for lying, though. He could say it was one of the guys at boxing practice, but he suspected Anna knew his schedule and knew that he didn't have practice that day. Billy winced as he remembered Anna knew about the event where Billy volunteered to train the moms. So basically he had to admit it was Karen or one of the other moms.

Or his own mom. After all, at least Anna already knew about those beatings. It seemed the safest.

"It was Mom, again," he said shamefully.

Anna slapped him lightly across the face. "Nice try, dummy. Mom was with me the whole day, remember?"

Damn his scrambled brain. He was no match for Anna's intellect on a good day, so this was just unfair.

Instead of giving her another answer, Billy started struggling to escape again. He bucked his hips, but the blankets hampered him, and Anna thrust her hips down against him and pinned him down again. He managed to get his right hand free for a moment, but before he could do anything useful, Anna had grabbed his wrist again, this time with both hands, and easily slammed his hand back down to the bedspread. In doing so, her head came down close to his, her lips near his ear.

"Tell me. Who. Beat. You. Up," she said quietly, with emphasis on each word.

Billy desperately didn't want to be where he was right now...even though Anna's firm butt felt amazing against his cock. Even though her grip on his wrists excited him. Even though her luscious cleavage was in full view. Even though his horny brain cried out for another knockout at his sister's hands.

It had gone too far. If it were just Heather and Anna, it wouldn't be so bad. But he needed to extricate himself from the Karen situation, and he needed to restore his reputation at the boxing club. And for that, he needed to escape Anna's pin without telling her who'd beaten him up. And preferably without Anna further weakening his already weak chin.

Billy bucked his body again, this time as hard as possible. Anna gasped and flew into the air. She smirked as she managed to land still pinning Billy, but then gasped again as her knee came down slightly off the bed. Anna tilted off balance, and Billy shifted his weight to throw her entirely off the side of the bed.

"Ooof!" Anna cried as she hit the floor on her stomach. Billy quickly swept the covers off him and rolled off the bed. He landed flat on Anna's back, causing the air to rush out of her lungs. While she was stunned, he quickly grabbed her wrists and secured her arms near her head. He put his legs on/around her legs to prevent her from getting up to her knees. His cock was nestled between Anna's taut butt cheeks, separated from them only by Anna's panties and his own boxer shorts. Her bare legs against his were turning him on even more.

For her part, Anna was loving this. Getting crushed and squeezed against the floor by her brother was getting her wet, and feeling his warm, hard cock against her ass certainly didn't hurt. And...sure, she might have preferred pinning HIM down, but this wasn't bad either. Billy was in control, but she was holding out. And Anna was starting to sense that he didn't really know what to do with her. She started to wriggle her body in an attempt to escape from him. She arched her back and stuck her butt out, rubbing it against his cock and making him moan right in her ear.

Billy wasn't loving it, at least not exactly. The physical stimulation Anna was giving him was as good as anything he'd ever experienced. But he was terrified that she might escape his grip, and that could lead to her punching him in the face and potentially knocking him out. So his arousal was drowned out somewhat by his fear.

Didn't stop his cock from being as hard as a diamond, despite having already cum twice this evening.

Anna kept squirming underneath Billy, squirming so fiercely that she was moving both of them backwards. Her tank top caught on the carpet and started riding up, revealing more and more of her sexy midriff. She started grunting and groaning, "Unh! Unh! Unh!" as she struggled to get her legs under her.

"Give up, Anna," Billy whispered in her ear, not wanting to wake Heather.

"No way! Tell me who beat you up and I'll stop," Anna whispered back, knowing exactly what he was thinking.

Billy was frustrated that he hadn't been able to subdue her yet. He had the weight advantage and the strength advantage, plus he was in the top position. But she was proving surprisingly powerful even from the bottom. Billy figured it was because he'd been weakened all day, which meant he needed to end this contest as quickly as possible. If Anna didn't want to give up from being crushed, he would **** her out from behind.

But just as he let go of Anna's wrists to get a rear naked **** locked in, she finally got one knee under her, and powered off it. Billy's hand brushed her taut thigh muscle and he almost came.

Billy tried to calm his mind and his dick as Anna's sexy body struggled against him. First things first--make her give up. Then maybe he could get some satisfaction.

They were now locked in a standing struggle, with Billy behind Anna. He modified his grip to a bear hug, pinning Anna's arms to her sides and wrapping his own arms around her chest. Billy squeezed hard, getting a nice groan out of Anna.

He looked over her shoulder and saw that his hold was almost making her breasts pop out of her little tank top. With her arms pinned the way they were, Anna couldn't do much. Billy squeeeeezed again, harder, and Anna's breath left her body in a gasp.

Billy brought his lips close to Anna's ear. "What do you think of that?" he whispered triumphantly.

Anna could only whimper in response. Billy shook her like a rag doll, in the process managing to get a tighter grip around her chest.

He tightened his grip yet again. "UGGHHH!" Anna gasped, tossing her head back, her hair flying around. Billy could feel her skinny arms straining against his grip, but they were no match for his muscular ones. He looked over her shoulder again. Her boobs were even more prominent, half-overflowing her tank top. He could see a delectable little crescent of pale flesh on each tit, undoubtedly the area that was normally covered by her bikini. He thought he could even see a tiny bit of her nipple on the left side. Billy relished the feeling of his hard cock pressing insistently into Anna's ass.

He was squeezing her too tight for her to breathe. Her little whimpers were getting quieter and quieter. Anna's head was drooping forwards and she was in a stupor. Billy knew she would have to either tap out...or pass out.