Heyo, made this story a while ago. Let me know if you like it.
(P.S Akito and Yuna are school bullies of Sana, they're going to be briefly mentioned)

"I love you, Riku"
Riku stared back into Sana's eyes. He loved her too, but he was unable to form words of his own. Sana simply smiled endearingly at his silence, and placed her palms on his cheeks. Slowly, she swept away his hair to look at her lover in a clearer light.
In the pre-dusk yellow sunlight, Riku looked almost angelic. His eyes were round and pure, and his expression was filled with genuine care. Oh, how I could embrace little Riku, Sana thought.In that instance, all of her memories of her home faded. All the memories of Akito and Yuna faded. Everything faded away except for her and Riku. In her perfect and beautiful world, it was just her and him together.
From the dozens of trees that surrounded them, crickets chirped happily - as if to reflect the unbridled emotion that Sana felt. Riku smiled as Sana held his face, and through his joyous expression, Sana could no longer hold herself back. Her back arched, as she leaned lower and parted Riku's lips with her own. The kiss was dry, but passionate. It was Riku's first kiss after all, so he stood on his tiptoes to reciprocate his love. But slowly, Sana pushed her tongue forward, and soon it slipped past Riku's lips. She rolled her tongue around, tasting her young lover's mouth. Heaven, was the only word that Sana could think of, as soon Riku's tongue slid onto Sana's. After a few minutes of their kiss, Riku pulled back, tongue hanging and gasping for air. Sana made sure to hold Riku so he didn't fall, she knew he must've felt drained after it was over.
But she knew it wasn't over, for she could see it in Riku's eyes. More, it begged. Sana couldn't help it, she laughed loudly. She was overjoyed that he was so eager, and the feeling made her feel warm with anticipation. He was only a child, but even children could hold indecent desires. She knelt down.
The shadows grew larger around the two, as the clouds above shielded the sun. Only a few rays of sunlight fell upon them.
Riku couldn't really understand what 'more' could be, he just wanted more of Sana's passion within him - although he couldn't possibly picture what that could be. He felt nervous and hot, even with the sun no longer directly shining upon them. However Sana knew exactly what more passion leads to, and she gripped the brims of Riku's pants. In one motion, she pulled down both his shorts and undergarments.
Riku's penis leapt out from the force of the pull, and stood straight, with it's tip pointed directly towards Hana's face. She smiled. She had seen this many times in the movies she had watched alone, but never in real life. But Riku's size made her feel non-threatened. His penis had a boyish innocence to it, unmolested and clean. Almost irresistable. She held her head closer to his member. Meanwhile Riku breathed even more heavily, still unsure to what Sana was about to do.
Slowly, Sana raised her hand to hold the base of his penis, and squeezed it gently. She heard Riku gasp deeply. Sana giggled at his reaction, and returned her gaze to his boyhood. She licked her lips. She was going to give him what others would call a blowjob - but Sana had never heard of the term, and it was only through her movies and her pure desire to taste Riku that she leaned forward and kissed his penis. Just like their kiss, Sana moved her tongue around the head, wetting it thoroughly. She tongued his member for a few minutes, and then slid her lips further along his shaft. Warm, Sana thought, as she took in the full length of the boy.
Riku had never felt this sensation, and unconsciously held the fringes of his shirt and pulled it above his stomach, as if to enable his lover even more. Her mouth felt wet and warm against his skin, and soon he panted in rhythm to Sana's own.
There was no guilt in Sana, for even she was too naive to recognize societal standards. As she moved her head up and down, tears streamed from her face. She was hopelessly in love with Riku, especially after what he had done for her that noone else had - which was to stay. This was her reward to him, in the most pure and pleasant way she thought of.
These thoughts filled Sana with happiness, and raw eagerness. As her right hand was tasked with holding Riku's base, her left hand began to move. As it brushed against her thigh, she placed it in between her legs. She reached down, and felt her vagina. It was wet with passion, and she shivered as she slipped her fingers into her vulva.

Five minutes passed, and soon Riku began to tense. He sensed something was about to come in his body, but he didn't know what to think of this. Sana noticed his tension, and quickened her pace. She wanted Riku to come. She wanted to taste his essence. She removed her left hand from her vagina, and placed it on Riku's stomach. She rubbed her hand quickly, in an effort to ease him into ejaculation.
Riku's breaths became more fleeting, and eventually, he sighed heavily in pleasure. Sana slowed the pace of her oral, and began to collect. His semen shot into the back of her throat and onto the roof of her mouth. She did not stop moving her lips however, as she wanted to empty his reserves. She wanted no one else but her to take Riku's seed. Riku was exclusive to her only.
Slowly, Riku's shots turned to weak squirts , to which Sana's head remained on his member. She tasted Riku's milk with her tongue. Riku's head sagged forwards, and he stopped releasing. He was exhausted from his first orgasm, and his hips began to buckle. Sana's arms sprung into action, and held the limp boy still.
After a minute of drinking Riku's seed, Sana pulled her head back. She looked up at him in nervousness. Had she rushed things too quickly with Riku? Had she hurt him in an effort to fulfill her own selfish desires? Will he no longer love her? These questions threatened Hana, and she raised her head to look at the boy.
Riku's gaze was already on Sana as she looked up, and on his face was an expression of happiness. Pure, childlike happiness.
Sana returned the smile weakly, and then broke out into a fit of laughter. He loved her, and she loved him.
That was what mattered.