Walking up the stairs felt strange to Robert. He only lost a couple of inches in the swap, but his overall body proportions where dramatically different now. Greta was a little bit taller than most girls her age an thereby a little lanky, which was perfect for the basketball team. This meant, his legs where probably a bit longer than his old ones, even though his new body was a bit shorter. The added feminine features in his chest and butt also factored into his shifted center of gravity. Nevertheless, he safely reached the upper level and eventually his bedroom.
After entering, Robert slammed the door behind him and let himself fall onto his bed. Laying there for a few moments, he became acutely aware of his current predicament. His changed lung volume when breathing in, the way his new heart beat in his petite chest, even the sound of his sister's former rumbling stomach where so unfamiliar to him. There was also the weight of his b-cup breasts, which shifted with every breath he took or movement he made. Not being able to relax like this, Robert decided to sit up and assess the damage.
With his legs spread in an unladylike fashion, Robert sat down at the edge of his mattress and looked down at himself, directly into his newly acquired cleavage. His perky b-cups where hold in place snugly by his sister's training bra, which in turn was covered by her yellow striped top. Carefully, he brought one of his hands towards them and began tracing their shape and feeling their weight. They where rather soft and pressing his fingers into them gave him a strange, unfamiliar sensation. Eventually he traced his fingers over his nipples, shocked by how much larger they where and how far they where distanced from his chest. As he kept probing them, he felt how they shrank together and became more sensitive, until two little nubs where visible though his top.
Embarrassed, Robert bit his lips and inspected his new arms instead. The skin felt so smooth and he noticed, how completely hairless they where. Perplexed, he noticed how thin they where. He lost pretty much all of his hard earned muscle definition. At the end of his feminine arms where his sister's former delicate hands, with which he did all his probing to this point. His fingernails where still short and cared for pretty well, but the yellow nail polish was something he definitely could not agree on.
With as much grace, as he could manage, Robert stripped out of his sisters top, leaving only the white training bra on his upper body. With one hand, he felt his flat, unfamiliar stomach, while he traced the curve of his thin waist and seemingly wide hips with his other. As his stomach-hand made it's way slowly nearer towards his crotch, his heart rate increased once again. Quickly, he got rid of his shorts as well, leaving him completely in his new underwear. Leaning forwards, as far as his sisters flexible spine allowed, he looked between his spread legs, to inspect his new anatomy. His panties where stretched across his smooth crotch, pressing tightly against his vagina. It felt rather eerie to Robert, to see something other than his familiar bulge down there. A slight cameltoe was visible, as his new labia pressed against the fabric of his panties. Carefully, he traced one finger along the slight slit, that formed on his underwear, cringing at the tingling feeling that went through his body as a result.
With shaking legs, he stood up from his bed and made his way over to his mirror. While he knew, what would greet him there, he was still quite shocked at the sight. Below his familiar, manly face, was his sister's smooth, girly body. He turned around a few times, to take every perspective of his new form in. On of the things that was bothering him the most, was how his shapely legs formed that feminine "gap", some women had between their legs.