Warning: This chapter contains vivid descriptions of sexual actions. So, if you don't like that stuff, get out.
Shadow knew about sexual intercourse. He knew how all different kinds worked. He knew how to pleasure someone and how to do certain...things. However, he had always thought it was simply for reproduction or pleasure. But now, he had found a third reason, love. He climbed on top of Sonic, a devious smirk on his face. His "ultimate life-form" instinct took over. He leaned in close, their noses touching. "Are you sure you're ready?", Shadow whispered. Sonic nodded. Shadow kissed Sonic briefly, before pulling away. "So, who's uke, and who's seme?", Sonic asked playfully.
"That depends, what are you comfortable with?"
"Anything, really."
"Then if you don't mind, I'd like to be uke." Sonic was shocked, he thought Shadow would want to be the dominant one. "I figure I'll let you be in charge for once." Shadow changed positions, so that Sonic was on top. "So go on, impress me." Sonic grinned. He went down Shadow's body, giving small kisses as he went. He made his way back up, and gave Shadow a warm, embrasive, kiss. "You know what you're doing.", Shadow said when they broke away.
"Just because you're always the one in charge, doesn't mean I'm unable to have some fun myself.", Sonic said, making small circles on Skadow's chest with his finger. He gave Shadow another quick kiss before going back to the real fun. Sonic went to Shadow's neck, giving him a bite to mark him as Sonic's. Shadow moaned slightly, and Sonic smirked. He had the ultimate life-form at his command, and he was going to utilize it to his full advantage. Sonic went down to Shadow's nipples, and played with one with his tongue, while massaging the other. Shadow moaned, "Sonic, that feels so good."
Sonic finished off with the foreplay and went to the main event. He went down to Shadow's fully erect member. It was rock hard. Sonic wrapped his hand around it and began to pump up and down. Shadow panted as Sonic increased speed. "S-Sonic I'm going to-" Sonic stopped. Shadow panted for more, but Sonic didn't want anything to happen prematurely. He placed three fingers in front of Shadow, "Suck." Shadow did as he was told, and when he was finished, Sonic turned Shadow on his front and put him on his knees.
He placed one of the fingers inside of Shadow. Shadow winced. Sonic slowly pushed his finger in and out of Shadow, until he was comfortable. He then placed the second finger inside, and repeated the process with the third finger. He had stretched Shadow out as much as he could. He waited to enter Shadow, "Shadow, are you ready?"
"Just do it already." Sonic entered Shadow slowly at first. He then pulled out and went back in, quicker this time. Shadow didn't feel pain anymore, just the pure ecstasy of Sonic inside of him. Sonic increase speed, this was amazing. He thrust in and out of Shadow, focusing on the pleasure. Then, Sonic hit the sweet spot inside of Shadow. Shadow arched his back and moaned loudly. "Sonic!", he screamed. Sonic sped up, he was nearing his climax, as was Shadow. Shadow screamed in pleasure as he finished off. This sent Sonic over the edge as well, and he released deep inside of Shadow. Sonic pulled out and laid down next to Shadow. "That...was...amazing.", Shadow panted.
"Yeah..."
"Sonic?"
"What?"
"I love you." Sonic and Shadow fell asleep in each others arms. Luckily, Tails had fallen asleep in his workshop and not heard a thing from the two lovers.