Looking for a doujin or hentai I saw years ago. Basically, a younger brother is turned into a girl by his older brother, who then dresses him up in a maid outfit and ties him up, raping him. I don't recall it being coloured, even a name would be enough to set me on my way.
Picture unrelated.
If it helps, he drugs his brother with a serum that he developed (the older brother was something of a scientist). He administers the serum in the milk of the younger brother, who was drinking it to hopefully grow bigger.