Starlight Glimmer had just shown up to Sunburst's family home. The pastel lavender pink filly approached the front door and gave it two knocks before just going inside. Starlight had been friends with Sunburst for so longthat his home was like a second home for her. 
 "Hey, Sunburst!" Starlight yelled through the hallway, "I'm bored; let's play a game!" 
 Starlight made her way through the house and towards the colt's bedroom. She neared the door and yelled "Sunburst!" as she quickly opened it, only to see an orange colt scrambling his sheets around in bed in a scuffle. 
"Oh- uhh, hey Starlight, I uh, I was just uh-"
"It looked to me like I just interrupted something fun," the filly said with a blush. 
 Starlight proceeded to walk into the bedroom, avoiding the scattered books around the room. While she was avoiding the books, the nerdy orange colt shuffled himself around, tucking away his new experience with difficulty, attempting to wrap his star cape around himself to conceal it. 
 Starlight neared the spot near Sunburst and giggled, "You're cute when you're horny." 
 Sunburst immediately felt his face burning and his heart beating hard and fast. He thought something was wrong, not knowing this feeling. 
 "W-what's horny, Starlight? I- I haven't heard about that in any of my books,"
 "Horny is what we ponies call the desire to breed. It's the thing that compels animals to reproduce," Starlight said, slowly walking towards the embarrassed colt. "You know how female animals have a 'heat' cycle?"
 "Of course I do, Starlight. I read my biology books," Sunburst said, shuffling his erection again. 
 Starlight noticed his immature colt cock shift and licked her lips subconsciously. Having just entered her heat this morning, Starlight was incredibly flustered. She had known all about the way she was feeling. She, too, had read her biology books. Unlike Sunburst, however, she had snuck into her parent's room and found her dad's porn magazine. It had pictures of stallions doing things with mares that had Starlight wanting to do those things herself. 
 Starlight stepped close to Sunburst and whispered, "I want you to claim me during my first heat," directly into his ear. 
 Sunbursts eyes opened wide, and he immediately began stuttering, not knowing what to say.
 The filly noticed that as soon as she said that, the young colt's first ever erection bounced and throbbed harder than it had ever done before, eliciting a soft moan from the nerdy pony. 
 "Starlight, I, uh, I think I'd like that," he said, being distracted by the filly turning around and exposing her flank. He had never seen anything like this before, not even in his books. Directly in front of him was a smooth,  virgin, almost dripping wet, filly pussy. Starlight's heat was so incredibly tantalizing to the colt that he couldn't resist the temptation to shove his muzzle into her heat. He immediately began lapping at the new sight and smell of a filly in heat, his cock throbbing underneath him. 
 "Oh, Sunburst, this is way better than anything I've ever thought!" the filly said through moans as her front legs started to buckle from the intense new sensation of pleasure. 
 As the colt was lapping at the filly's virgin slit, his cock began to twitch more than it already had been, and a drop of precum formed at his flare. His nerdy mind was entirely incapable of thought, fully consumed by the hormones and lust of a filly in her first heat. Sunburst was running on pure instinct, but that didn't mean he knew what he was doing. He was sloppily lapping at Starlight Glimmers pussy, drawing out moans from the filly when, through a moan, she says, "Let's go all the way, Sunburst." 
 Starlight had to practically kick the young colt off of her, so she could move into a better position. Once Starlight turned around to move, she saw the other young pony sitting down, staring at her flank while rubbing his erection with his hooves. 
 "I-I'm sorry Starlight, I just- I don't know what's gotten into me," Sunburst said timidly, turning his face away as he took his hooves off of himself. 
 "It's alright; fillies mature sooner than colts, so this is all probably very new to you," Starlight said as she sat down next to the embarrassed colt. "But I snuck into my dad's bedroom and found one of his grown-up magazines and did some of my own research. It's actually the game I wanted to play with you, and my timing couldn't have been any better."
 Sunbursts erection showed no signs of softening as the filly explained herself to him. 
 Starlight then stepped towards the colt and pushed him onto his back gently, his cock pointed to the sky. 
 "Starlight? What are you doing?" The young pony asked nervously. 
 "I'm going to make us both feel great," the precocious filly replied
 The lavender pink pony then returned the favor for the oral received just before. As she opened her maw and began to cover the tip with her lips, Sunburst moaned loudly, and his cock twitched excitedly. The filly began to move lower onto the colt's immature erection, begetting heavier and heavier moans from the colt. Once Starlight got to the point where his flare was tickling the back of her throat, Sunburst made an involuntary twitch of pleasure. Having never felt anything like this before, the colt began to subconsciously buck his hips back and forth slowly.
 He didn't quite understand what was going on, but he knew enough to know it felt good. 
 "Oh my goodness, Starlight!" he moaned in pleasure as he neared his very first orgasm. 
 Hearing that, Starlight took the colt's flare out of her mouth, and started to crawl on top of Sunburst. Aligning herself so that she was upright, she put her rear legs on the ground. 
 "Starlight, w-what are you doing?" The colt asked, desperate to reach climax. 
 Her virgin slit resting along the length of the immature cock underneath her, subtly lubricating it. Once in place, the filly started to rock her hips back and forth along the colt, spreading her natural heat along his cock. 
 "You're gonna breed me," Starlight had said, staring directly into the eyes of her friend and now lover. 
 Upon saying those words, the filly moved up a little, reached down, and positioned Sunburst's underage cock directly against the slit of her virginity. 
 Taking a deep breath, Starlight slowly moved down and felt his tip pushing against her tight entrance, and then they both felt it; the flare went in. 
 "Oh Celestia!" the filly said, feeling her slit be parted for the first time in her life. 
 Starlight began slowly shifting down further, and the pair both felt her hymen tearing around him. Starlight let out a yell of pleasure as her best friend had claimed her. Sunburst had let out a guttural moan as he was penetrating deeper inside of her, feeling her flower burst because of him. 
 As Starlight sat down all the way, a moan escaped both of them as she began to quiver in pleasure at the newfound sensation of her pussy being filled. 
 "S-Starlight, I feel s-so good right now," the colt had said as he felt himself go further inside of her. "I've n-never felt like this before," he continued as his cock throbbed inside of her, forcing out the few drops of hymen blood. 
 "This is so much better than anything I'd ever imagined!" Starlight exclaimed in pleasure as she leaned in to kiss the colt in front of her and sat down all the way, taking him to the hilt. 
 During the passionate kiss, the filly took the lead with her hips and started bucking back and forth. Following her lead, the colt began trying to match her movements. Instincts alone fueling their lustful actions. 
 The kiss broken was by a confused colt nearing orgasm. His moans and awkward movements were a telltale sign that Starlight was doing a good job. 
 The filly began riding Sunburst like a rodeo bull. Her hips were bucking wildly up and down on top of the virile male. 
 Sunburst was feeling pleasure he had never experienced before, and he was loving every second of it. With each thrust, the colt approached closer to his first orgasm, until shortly after he screamed, "Starlight! I think I'm gonna pee!" 
 Starlight shut him up with a kiss as she slammed down onto his hilt, drawing him to his orgasm. 
 Sunburst was moaning into the filly's mouth and kicking his legs on the ground. His eyes rolled into the back of his head, and his cock started throbbing, and he reached his orgasm. With each throb, a heavy spurt of cum shot inside his partner.
 Starlight had also reached her climax as she felt his immature semen filling up her womb.  
With Sunburst still inside of her, the filly leaned forward and hugged him heavily, starting a new kiss. 
 The afterglow of their first time was a heavenly feeling. Both ponies were spent, and they held each other in the warm embrace of their arms and slowly drifted off. 
Meanwhile, the filly's eggs were being fertilized by the fertile sperm inside of her.