Frisk's "back pocket"

The afternoon sun over the Surface was relentless, a golden weight that pressed down on Frisk’s shoulders as he trekked through the wooded trails near the base of Mt. Ebott. Now a teenager, Frisk had grown significantly since his time in the Underground, but he still possessed that same restless curiosity that had led him down the hole years ago.

Today, however, he was mostly just miserable. The humidity was stifling, turning his striped shirt into a damp second skin and causing sweat to pool in the small of his back. He was a growing boy, and with that came a certain pungent musk that he hadn't quite learned to manage yet. He smelled of salt, earth, and the lingering scent of the onions he’d had on his burger for lunch.

He was about to turn back toward the monsters' settlement when he saw a flicker of movement near a patch of golden flowers. He leaned down, squinting, and his eyes widened.

It wasn't a monster he recognized, nor was it a human child. It was a boy, no larger than Frisk’s middle finger, dressed in tattered green fabric. The tiny creature looked up, his face pale with terror.

"Please," the tiny boy squeaked, his voice like the chime of a very small bell. "Don't step on me."

Frisk knelt, his knees cracking. "I won't. Who are you? Where did you come from?"

"My name is Venus," the boy whispered, trembling. "I... I got lost. I don't know how I got so small. Everything is so big and loud."

Frisk felt a surge of protectiveness. He couldn't leave someone this small out here; a hawk or even a large beetle could finish him off. He reached out a hand, letting Venus climb onto his palm. The tiny boy felt like a dandelion seed, weightless and fragile.

"I’ll take you home," Frisk promised. "I just need to... wait."

Frisk patted his sides. He was wearing his favorite pair of athletic shorts, the kind with the built-in mesh liner, but they lacked pockets. He looked around, frustrated. He couldn't carry Venus in his hand the whole way back; he needed his hands to navigate the rocky descent, and he was already slipping on the loose dirt.

"I don't have anywhere to put you," Frisk muttered, his brow furrowed. He looked at his waistband. It was the only secure place. "Look, Venus, this is going to be weird, but it’s the only way you’ll be safe while I climb down. I’m going to put you in the back of my pants. Just hold on to the elastic."

Venus’s eyes went wide. "In... in there?"

"It's just for the walk," Frisk said, feeling a flush of embarrassment that rivaled his heatstroke.

Without waiting for a protest, Frisk gently pulled back the elastic of his damp underwear and shorts. He carefully lowered Venus into the space behind him. As he let the elastic go, the fabric snapped back, pinning the tiny boy firmly against the heat of Frisk’s skin.

Venus let out a muffled gasp as he found himself pressed directly between Frisk’s sweaty asscheeks. The sensation was overwhelming. It was dark, incredibly warm, and the smell of Frisk’s teenage musk was everywhere—a thick, salty aroma of sweat and denim.

"You okay back there?" Frisk called out, already starting his jog back toward the house.

"It's... very tight!" Venus yelled back, though his voice was swallowed by the fabric and the rhythmic thumping of Frisk’s stride.

Every step Frisk took caused his muscles to shift and flex, squeezing Venus like a living vice. The boy was trapped in a humid, fleshy canyon. The sweat from Frisk’s