Your yandere girlfriend moved in with you, after you managed to calm her shit down. Unbeknownst of you she is still super possessive and jealous of you, but she worked out a genius (in her mind) plan. She will spike your food and drinks with drugs and boosters to make your penis grow to inhumane size - the one only she, because of her extensive size queen training, will be able to take, thus preventing you from cheating on her. Brilliant plan.