Against their consent, a character is subjected to the techniques and methods that over the course of the VN change their sexual orientation.

The usual case involves a gay character accosting a straight victim, and use hypnosis, magic, sci-fi technobabble or simply raping/mindbreaking them into becoming gay.

The reverse scenario of a gay character becoming a victim of a straight attacker and being "straightened out" is also possible, but much rarer in fiction due to the negative real world connotations.

Sometimes the change is not full, and the character becomes bisexual, instead of completely changing their orientation.