She'd called me aside again.
 
>"So Anon, I hear you've been getting shitty grades in school again."
"So? Whats it to you?"
>"Oh nothing, just want my baby bro to do his best."
"Come on, stop teasing me! I'm not a little kid any more!"
>"Aww, you're so cute when you're indignant. Come on, tell me whats the matter.. We're close right? You can trust me.."
"Well, I mean.. There are these cute girls in class, but, I don't think they're interested in me."
>"So its girl issues huh?" 
She slipped behind me, her superior reflexes caught me off guard. She hung over me with an arm around my shoulder. The other slipped its way into my pants.
She grabbed my dick feeling its fleshy mass in her hand.
It was hot on my junk, I couldn't help it becoming erect as her breasts were pressing up against my back.
>"You've been thinking with this haven't you?"
I blushed heavily, her hands still violating me, with her giving me a seductive grin. I managed a hushed,
"Yes.."
>"Poor thing, it's not easy to focus with all the cute girls around." 
She said running her hand up and down my shaft.
>"Do you want big sis to help you focus more on your studies?" 
My dick fully erect in her hands I couldn't resist her. I nodded quickly.
 
She slipped her hand out of my pants walking in front of me. She flipped her hair back as she got down to her knees. Even through my pants my dick remained pathetically hard.
She unbuttoned the top button of my jeans slowly pulling the zipper down revealing my boxers.
With my boxers still on she rubbed her index finger in a circular pattern around the middle of the shaft. I winced in pleasure as she did.
"Do you promise to focus on your studies if I do this for you?"
"Yes, yes I promise." I said in desperation.
She slipped her fingers around the elastic of my boxers pulling them down exposing my dick. She took her finger placing it at the tip of my dick pulling it alll the way down before letting it go watching it spring back up. She giggled.
She ran the tips of her fingers up and down the length of my dick. Each one like a small pocket of orgasmic pleasure exploding as her fingers made contact with my cock.
"Do you like what big sis is doing?"
"Y-yes, it feels good."
She smiled brightly at me.
"I'm glad."
She hugged my lower waist, my dick pressing into her shoulder a bit.
"Um.. Sunset, why are you doing this for me. I mean, not that I don't appreciate it, because I do its-"
"Shh, I just wanna help my cute little bro out."
"Really?"
"Truth is, I kinda already knew you were striking out. I figured you might be lonely, and, then I saw your grades. I figured if I helped you out, maybe you'd wanna focus on your studies a little more."
I'm not sure what it was, but something about what she said caused me to tear up a little. She rose up standing  and wiping the tears from my eyes. She embraced me with a full frontal hug, my pants still around my ankles like a dork.
"I love you Anon."
"I love you too Shimmy." She put her hands on my shoulders kissing me, our mouths became one. The sweet taste of something like bubblegum.
She made her way down south again running her hands down the course of my chest, stomach, and thighs.
Down on her knees again she began to stroke my cock. A bit of precum came from the tip, she took her finger poking the bead, pulling letting it form into a strand. She licked her finger with the cum on it.
"Yummy." She smiled before diving into my cock. The wet suction of her mouth felt amazing. She sucked the head a bit before pulling off with my cock her hand and licking the shaft from the base to the head.
"You like it when big sis sucks your cock like this?"
"Mmm yes." I said.
"Go ahead, I want you to enjoy this. Don't be shy, make your sis take your dick, put your hand on my head and thrust into me."
I pulled her head into my dick thrusting into her mouth. The lewd expression on her face as I thrusted into her. I couldn't take it any more, I came inside. I pulled out, semen dripping all down her chin as I did.
>"Do you want sis to swallow your cum?"
"Yeah, swallow." She did taking in every bit of it. I just made my sister swallow my jizz. Why did I do that?
In that instance started to freak.
"W-what, what am I doing." Sunset got up putting her hands on my shoulder.
"You did really good Anon. Maybe now you can focus more on your studies." She started to leave.
"W-wait! Um, thank you.. That felt, amazing.. I.. I-" She put her finger to my lip.
"I know. But you made me a promise, you'll keep the promise you made to me won't you?" I sighed deeply.
"Yes Sunset." She put her hand on my head ruffling my hair.
"Good boy, make sure you catch up on all your homework."
"I will!" I said obediently.
She smiled turning the corner and walking away.
I paused thinking for a moment. Dammit, I had a lot of homework to do. This was gonna take me all night at least. But, I couldn't break the promise to sis. I sat down and scratched my head as I did my homework, and for the first time in a long while, I didn't feel distracted at all.