Ethan was paralyzed by seeing the monster. But to his surprise, he didn't feel fear so much as a confused mix of feelings. Fear was just one of them. It was mixed with confusion, curiosity, and... arousal? He kinda didn't want to admit it, but he was weirdly attracted to this creature.
Suddenly it moved toward him, and he realized it didn't have limbs but tentacles. Oh fuck, he realized. Tentacle sex was a secret fantasy of his, and while he usually preferred seeing girls on the receiving end of it, he couldn't pretend his body wasn't fascinated by experiencing that for himself. A tentacle reached for his waist and forcefully pulled off his boxers and pajamas, and another yanked off his T-shirt, leaving him naked as the day he was born. The tentacle that had grabbed his lower end now clung to one leg, and a second one joined it to spread him, his hard cock now out to the monster. He felt his arms quickly bound by two other tentacles, and another moved to fill his mouth. He couldn't get out of this thing's grip if he tried, and oddly he didn't feel too desperate a need to.
The monster finally started its real goal, and Ethan gasped as he felt a tentacle move for his dick- and felt an incomparable clinging and sucking. As a virgin, he couldn't say for sure, but he assumed this was pretty close to what a pussy felt like. Next, a tentacle came for his butt, and he winced as a soft slime coated the tight ring of muscle- and promptly loosened it up, the tendril pushing inside him and slowly thrusting in and out in a motion he found surprisingly pleasurable.
Despite the thrusting of the tentacle in and out of him and around his cock, the monster wasn't done with prying pleasure from Ethan. It extended two more tentacles to play with the boy's nipples, and he was surprised at how pleasurable the teasing felt. Suddenly, the tentacle in his mouth started pumping back and forth, forcing him to suck it; weirdly, it tasted kinda good to him. Not that he had a choice to suck, as another tentacle gripped his throat, the asphyxiation clouding his mind and only adding to his pleasure.
Pretty soon after, in no small part due to the tentacle in his butt rubbing against his prostate and the walls around his dick squeezing his head, Ethan hit his peak, and came hard into the tentacle around his shaft. In response, the monster came too, and Ethan felt the tentacles spasm around him, the ones in his mouth and ass seeming to shoot some liquid inside him. As the tentacle around his neck released its chokehold, he swallowed the liquid from the tentacle, and in his ass it had already seeped into his body.
The tentacle beast vanished almost instantly, but Ethan was gonna keep feeling its effects.