Disclaimer: I do now own Inuyasha or any other characters (except Katsurou).
Elven
Kagome's attention was brought back to Katsurou, when she felt the first stirring of his youki rising. She stepped away from him.
His entire person pulsed with energy. His transformation happened in a wave that started at his head and went all the down his body. His black hair faded to silver. His dog ears, disappeared and were replaced by elven shaped ears. His eyes bled to red; a purple stripe appeared on each cheek.
He cried out as his nails grew into sharp claws. He dropped to a crouch and snarled at them, showing his fangs.
Sesshoumaru's eyes grew wide in shock. The child had not reverted to a fully human state, like his father did. Instead, he turned completely demon.
Katsurou was consumed by demonic bloodlust.
Mindlessly, he launched himself at Rin.
Please review :D