Bobby realized then what he was turning down. "Wait," he said, gently pushing Katie off his cock. She looked devastated for a moment- but then he pushed her down onto her back, and smiled before kissing her, his cock rubbing along her tail. "I think I wanna do this after all."
"You're not scared about the risk?" asked Katie.
"Yeah, I am, but... I feel like I have to do this right now," Bobby breathed, his head kissing her slit. "My body needs it."
Katie smiled, and then gasped with satisfaction as Bobby's shaft entered her mermaid pussy. The boy started thrusting instinctively in and out of her, his hands grabbing at her boobs to try and get her as excited as her. The two panted and moaned messily as they fucked, and the touch of Katie's webbed hands on his back and her tail against his crotch and legs and butt excited Bobby even more.
Not surprisingly, Bobby didn't last that long- the prior teasing, his mermaid fetish and the fact this was his first time meant it wasn't long before Katie's soft, wet body brought him groaning to his climax. His hips and legs stiffened and shook, and he shot several loads of cum deep inside Katie while her walls clenched around him in her own orgasm, kissing her eagerly once both of them had finished cumming.
"Was that good?" he asked shyly.
"Of course," Katie smiled, kissing him more. The human and the were mermaid fell asleep contentedly in each other's arms on the deserted beach. But as they slept, their bodies would start to change...