Pact with a Witch / Pacto con una bruja
Your roommate and best friend tries to rape Neus, the most introverted girl in the whole design school, who bites him just after you save her.
You discover that bite was not only for self-defense. It also contains a curse that turns your roommate step by step into a girl. With every day that passes, he seems to forget more of his past and becom more attracted to you.
To save your friend, you make a pact wit Neus to have 4 dates, and the last night she promises to return his original male form to your buddy. Although it seems that she keeps her word, there are sinister things she had not told you yet.
[Edited from Lemmasoft thread]