Noshiro was outside on the second floor balcony of the admin building, enjoying the bright and sunny day. It had been a busy few days for her, so she was glad to finally have a chance to relax and enjoy the sun. She closed her eyes and just appreciated the warmth and the chirping of the birds.
The door behind her opened and she looked over her shoulder to see her sister, Agano, coming up behind her. "Oh, hello Agano-nee. How are you today?"
"Hi, Noshiro. I'm doing great today, thanks! Kinda need your help a little, though" Agano said. Noshiro was bent over the railing of the balcony, her butt jutting slightly, and Agano took advantage of this by grabbing onto her thighs and pressing her hips to Noshiro's bottom.
"Geez, Agano-nee! Stop stroking my thighs!" Noshiro complained. Agano's hands rubbed up and down her sister's hips, and Noshiro could feel Agano's cock hardening against her backside. "I guess you want to do it the way we normally do it, yeah?"
"Mm. Yeah" Agano said. She lifted up the back of Noshiro's skirt and a moment later Noshiro felt her sister's cock wedged up her butt crack, rubbing back and forth across her panties. Agano's hands found their way to Noshiro's butt and she started groping and fondling her, and Noshiro hummed at the touch. After a few minutes Noshiro felt a cool touch of fluid on her lower back and realized Agano was leaking precum onto her.
"Agano-nee, you're making a mess" Noshiro said, and Agano stopped rubbing.
"Huh? Oh wow, I really am. Uhh, sorry, but... You're kinda gonna have to wash these once I'm done" Agano said, and Noshiro could only imagine how much her sister had leaked onto her. "I'll put on a condom, gimme a sec."
Noshiro waited patiently while her sister applied a rubber to herself and suddenly she felt a prodding at the back of her thighs. She yelped when Agano's cock was suddenly thrusted between her thighs, the tip of it sticking out far enough that Noshiro could see it. She looked over her shoulder at Agano, who just smiled. "Least with a condom on I don't have to worry about spurting onto someone's head as they walk out the first floor."
Noshiro blushed at the implication and turned back. She hung her head as Agano started thrusting, the top of her cock rubbing against Noshiro's pussy through her panties. It was a pleasant feeling, though not really enough to make her cum or even to make her wet. Still, it felt nice. Agano and her had sex often enough, with Noshiro having marks only for vaginal, but she didn't mind Agano sticking her cock in her buttcrack or between her thighs. It kept things a little more exciting than just missionary and prone-bone.
Noshiro felt Agano's breasts press to her back and her arms wrap around her stomach. Agano put her chin on Noshiro's shoulder and Noshiro smiled. "Having fun?"
Agano let out a sigh in response and tickled Noshiro, which made her squirm. Her sister's hands slid under her shirt to her breasts, and Noshiro yelped. Agano giggled and just held onto Noshiro's boobs as she thrusted back and forth between her thighs. One of Agano's hands left her breasts and slipped into the front of her panties to rub her clit, which she appreciated.
"Mmm, Agano-nee, thank you. I like the way you rub me" Noshiro said.
"Hehe, glad to hear it. I love how smooth your thighs are, and how plump your cute butt is. Makes for great cushioning while I do this" Agano said, and Noshiro blushed.
"Geez, Agano-nee, don't say things like that about me. It's embarrassing."
Agano apparently had nothing to say to that, instead quietly focusing on her thrusting. Noshiro looked down and watched as her sister's cock slid back and forth, appearing and disappearing over and over again. She rubbed her knees together, the sound of Agano's labored breathing filling her ear.
"He- Hey, what if I... Instead of cumming in the condom, I pull back and cum on your little butt?" Agano said.
"You want to...finish, on my bottom? That'd make such a mess, though" Noshiro said. "I'll let you do it if I can keep my underwear on, got it?"
"Yeah, sure thing" Agano said. She pulled back and a moment later pushed back in, her cock now bare, still glistening from the condom's lube. After a moment Agano huffed, apparently struggling, and stopped. "Hey, can I pull your panties down?"
"Agano..." Noshiro said.
"The lube's soaking into your undies, but if you're wet then I can keep going" Agano said. Noshiro thought about it a moment before she nodded.
"OK, but pull out before you finish, OK? That way I have time to pull them back up" Noshiro said. Agano tugged her panties down and Noshiro held her knees together to keep them in place. She gasped at the feeling of Agano's cock rubbing back and forth across her bare pussy. She looked down and saw precum smeared on her thighs and licked her lips, kind of wishing Agano would stick it in her. Her sister had a pretty high libido, so she was pretty sure they'd be having sex again later, but that didn't do much to placate her arousal now.
Still, Noshiro held on for Agano's sake. She listened to the shlicking sound of Agano's thrusting, her sister's mouth pressed to her shoulder to stifle her moans. Agano's hand left Noshiro's panties and just held onto her stomach, her other hand still on one of Noshiro's boobs. Agano was letting out short, shallow breaths through her nose on each thrust, and Noshiro smiled. Agano had a high libido, yes, but she also had a short fuse, so Noshiro knew from experience that her sister wasn't going to last much longer. "Enjoying yourself~?" she asked.
Agano moaned into her shoulder and kept up her thrusting, her pace erratic and frenzied, desperate to pump out her load. She thrusted and thrusted, and Noshiro turned to look at her sister. Her cheek bumped into Agano's nose, and Agano's eyes fluttered open. She closed them again, her brow furrowed and face flushed. Noshiro grabbed onto the waistband of her panties to prepare herself when suddenly she felt Agano's cock pop out from behind her thighs. Agano screamed into her closed mouth and Noshiro pulled her panties up, the warmth of her sister's spunk hitting her bottom a second later. Agano stroked and stroked, the tip of her cock pressed against Noshiro's butt as her cum spurted onto the white cotton, and when she was done Agano put her forehead on Noshiro's shoulder.
"Hah... Thank you, Noshiro..." Agano said, panting hard. Her load was big enough that Noshiro could feel it through her underwear. She squirmed at the feeling and Agano rubbed her tip up and down one of her cheeks for a bit before she finally released her. Noshiro flipped the back of her skirt back down and turned around, and Agano suddenly kissed her. She hummed and kissed her back, and Agano held her against the railing as they made out.
After a few minutes Agano was done and she pulled back, her hands still on Noshiro's hips. "OK, all done. Thanks again, Noshiro-nee. I gotta go, so I'll see you back at the dorm."
"Bye, Agano-nee" Noshiro said. Agano made herself decent and took off, and Noshiro left the balcony a moment later. The warm wetness on her panty-clad bottom was starting to become uncomfortable, so she headed straight back to her dorm building to change and get her underwear into the laundry. Once she was done she still had the rest of the day ahead of her, including another session with Agano to look forward to, and she smiled. A good day was going to be even better before she knew it.
Although, she figured a bath would also be a good idea, as well.