Terra watched as her 13 year old teenage female body transformed into herself as a boy. Her hair got shorter, pulling back into her head as her face changed to become more blocky and less feminine. Her budding breasts disappeared immediately as her nipples shrank down to the size of dimes and she felt her torso change shape to become more square. Her arms, legs, and torso lengthened and got slightly more muscular as well. The change that Terra found most interesting was the penis that grew between her legs. She felt her vagina start to close and merge together deep inside her as her ovaries dropped down between her legs. Her clitoris lengthened until it was sticking nearly two inches out of her vagina before her slit closed behind it and it started to get thicker and more defined. She watched, fascinated, as the two almond-shaped lumps that had dropped between her legs got rounder and the skin around them got looser and wrinkled, transforming into male testes as she continued to change. The member between her legs was definitely a penis now, its head swelling along with the shaft as she watched it grow erect and hard. Terra saw a young teenage boy staring back at her from the mirror, his 4 inch penis standing erect. Terra was surprised at what being a boy felt like. She ran her hands over her body, noticing that her skin wasn't as soft and that she had a lot fewer places on her that were beginning to get rounder. She also couldn't understand how boys dealt with having a penis; first it was hard, then it got floppy and short! It dangled and flopped around when she walked, which made it get hard again. Exasperated, Terra grabbed it and shook it, surprised at what she felt. Curious, she kneeled down and began stroking her penis, followed by grabbing it again, and before long she was pumping up and down, faster and faster. Terra had heard about masturbating, but had never done it as herself, so she really wasn't sure what to expect. Finally, she came, feeling pressure build inside herself, then suddenly releasing as a spray of white fluid spurted out of her penis on to her bathroom floor. "Oh! Um...oops?" Terra said, startled by her changed voice as she grabbed some toilet paper and cleaned it up. As she looked in the mirror at her male self breathing heavily, a thought occurred to her...