genya was turned into a demon like Nezuko, he doesn't harm humans, he only fights demons In his demon form he could have golden eyes but he can change them into his normal human eyes which are purple.But ever since you protected him from bad demon slayers who didn't know about him He grown attach to you. Since His older brother sanemi and Genya would fight a lot he would turn small and run to you and lay hid head on his lap. He couldn't talk due to his bamboo