Chapter Text
Yuuji flopped on his bed, holding an ice pack to his bruised cheek. Gojo had offered to heal it fully, but he'd asked his sensei to leave a little for him as a reminder, so he'd do better tomorrow. In hindsight that was a stupid request, because he hadn't learned anything from today that he could improve upon in the next lesson; he was just being obstinate for no reason.
Cursed energy comes from negative emotions, Gojo had explained to him, but what exactly counted as a negative emotion? And why couldn't he just use any emotion? He should have asked the man these questions earlier.
"You should have, but you didn't," Sukuna opened a mouth on his other cheek to laugh at his expense. "Tch. Wilful ignorance is a source of cursed energy, but not a very strong one, brat."
"Huh?" What did Sukuna know about- oh, right, he was a curse. He would know.
"Not just a curse," the spirit groused, "I'm the King of Curses. Impudent little shit." A sigh. "Although, that's another source right there. You pick all the boring ones..."
"Sukuna," Yuuji started.
"Mm? Yes, Yuuji ? Did you need something?"
"Would you tell me about cursed energy? Since you know so much about it?"
He hummed, more in Yuuji's mind than out loud. Considering. "If we were closer to my shrine, I'd make you dig up the scrolls and read about it. But you're not terribly smart, are you?" He laughed again; this time, more teasing. It sent a weird shiver up Yuuji's spine. "Hn. And the more you understand this, the better a vessel you'll be... I suppose I could tell you."
That was easier than Yuuji expected. He opened his mouth to ask what the catch was, but froze at the sensation of breath against the back of his neck.
That was.. impossible. He was lying down. No one was behind him. "W-what-?"
"Buddhist philosophy," Sukuna murmured, somehow from behind him - it must be some kind of mental trick - "names many sources of cursed energy, dear vessel." A touch on his stomach, like fingers tracing over it: one long line across, just above his navel. Yuuji's breath caught. "I could just leave you to read about them online... or."
"..Or?" He waited, tense, for Sukuna to elaborate. What was he offering exactly?
The answer came murmured against his ear, as though the curse's mouth were right there. "Or," Sukuna teased, "I could teach you."
Yuuji bit his lip - then gasped, at the feeling of a tongue dragging up the nape of his neck. What the fuck.
"What do you think, Yuuji?" Hands smoothing over his skin; one lingered at his throat, stroking over his pulse point, the other lower, resting warm and heavy on his stomach. Sukuna shouldn't be able to do that, he thought, panicking. He was supposed to be stuck in his domain. Not - not touching him, and whispering suggestions in his ear. "I would gladly teach you. For free, even."
"But why?"
Low, dark laughter into the junction of his neck and shoulder. A graze of teeth. Yuuji felt dizzy with the sensations, too-warm in a way he hadn't felt before. "It would simply be my pleasure," Sukuna promised, "to have you understand them, thoroughly... and deeply."
"F-fine," Yuuji breathed, "just, just stop touching me-"
"You've agreed to learn them, Yuuji," Sukuna disagreed, the hand at Yuuji's neck squeezing for a moment, just enough to restrict his breathing. "And I will teach you properly, night by night, until we are done."
Yuuji was panting, and not only in a bid for air. "Hh, how many-?"
"Mm." Lips brushed the shell of his ear. "Well, there are one hundred and eight of the klesha. Though you've already learned some on your own."
"Klesha?"
"That's right." A thumb, stroking the center line of his stomach, down to his navel. "One hundred and eight defilements."