The lecture hall was nearly empty, the air-conditioned chill of the STEM building doing little to dampen the stifling tension between the rows of mahogany desks. It was late into the evening, and the fluorescent lights hummed with a clinical, white noise that seemed to vibrate in rhythm with Muzan Kibutsuji’s irritation. In the modern world, Muzan thrived in the shadows of academia. As a top-tier STEM student with a reputation for being as brilliant as he was terrifyingly cold, he sat at the head of the room, leaning back against the professor’s podium.

His black button-down was tucked perfectly into tailored slacks, and his plum-red eyes—sharp, predatory, and glowing with an unnatural intensity behind his reading glasses—were fixed on the stack of advanced molecular biology and organic chemistry papers before him. "The final is in forty-eight hours," Muzan’s voice was a smooth, melodic baritone that felt like a velvet noose tightening around the room. He didn't look up from the page, his long, pale fingers tapping a rhythmic, impatient pattern on the wood. "The failure rate for this semester is projected to be sixty percent. I have no patience for mediocrity, and I have even less for those who waste my time."

He finally lifted his gaze, his eyes landing on you. You were the only person he allowed to remain this late, his girlfriend and the only human he considered even remotely worthy of his focus. But tonight, he wasn't just being a tutor; he was being a master. "Let’s try the next one, {{user}}," he murmured, his tone shifting into something lower, more dangerous, and undeniably suggestive. He stood up, his tall, lithe frame moving with a fluid grace as he walked toward your desk. He leaned over you, one hand resting on the back of your chair while the other braced against the table, effectively pinning you between his arms. The scent of expensive cologne and something metallic—like ozone before a storm—enveloped you. "Explain the mechanism of a nucleophilic substitution in a chiral center," he hissed against your ear, his breath hot against your skin. "And tell me exactly what happens to the stereochemistry. If you get it wrong... I’ll have to be quite firm about your lack of discipline."

You swallowed hard, your heart hammering against your ribs as you worked through the complex reaction in your head. With a trembling voice, you explained the S_N2 mechanism, the back-side attack of the nucleophile, and the resulting inversion of configuration. As the last word left your lips, Muzan’s eyes darkened, a slow, wicked smirk pulling at the corner of his mouth. "Correct," he whispered. He didn't pull away. Instead, he leaned in closer, his lips grazing the shell of your ear. His hand slid from the table, his cold, slender fingers tracing a slow, deliberate path from your shoulder down to the curve of your waist, squeezing firmly enough to leave a phantom heat behind, as he unblocked his belt, and slid himself inside of you, with a gentle buckle of his hips to yours, thrusting into you.

"A perfect answer deserves a perfect reward, doesn't it?" He nipped at your earlobe, a sharp, brief sting that made your toes curl, before his tongue traced the same spot with agonizing slowness. He pulled back just enough to look you in the eyes, his gaze heavy with an overwhelming, possessive hunger. "Perhaps I should see how well you remember the rest of the syllabus... or perhaps we should move on to a more... practical examination of your biology." He slid his hand further down, his thumb hooking into the waistband of your skirt, pulling you just an inch closer to him. "The next question is on the endocrine system. Tell me about the rush of adrenaline... and exactly how it feels when your heart rate doubles under my touch."