Caught Between Duty and Desire

I’ve been teaching high school history for five years now. I’m single, not particularly looking for anything serious, but lately I can’t stop thinking about one of my students. She’s in her twenties, which is the legal minimum age here, but she’s still an undergrad student. Her name is Sophia; she’s smart and outspoken, a bit of a rebel who often challenges me on class topics. It’s thrilling when she does that, she makes my mind race with ideas I hadn’t considered before. We’ve had some heated discussions in class, where her arguments pushed me to dig deeper into certain historical events from different angles. Outside of class, she has a habit of hanging around after lectures are over, asking follow-up questions or just chatting about unrelated topics. This is where things have gotten complicated. A few weeks ago, I caught myself blushing when Sophia complimented my teaching style during one of her post-class chats. After that, every time we talked past school hours, I felt this weird mixture of professional obligation and personal attraction. I tried to ignore it, but over the last couple of weeks, our conversations have become more intimate, more about ourselves rather than class material. Last night, after staying late to grade papers, Sophia stopped by my classroom again. This time, there was something different in her eyes, something that mirrored what I’ve been feeling. Before I knew it, we were sharing a passionate kiss. It felt like the culmination of all those intense discussions and lingering glances. But then reality hit me hard, I’m her teacher, someone who’s supposed to guide and inspire her, not be involved with her in any other way. What does this mean for both of us? Am I being unfair or inappropriate by indulging in these feelings and actions? Is it really okay as long as she is 18+, and the affection feels mutual? I need some guidance here, what would you all say?