"Snape... You actually learned that Snivellus's magic?"
At Kyle's words, Sirius remembered where he had seen that blade-like curse before.
More than ten years ago, just after they had graduated, Snape—still a Death Eater then—had used that curse against them.
Too much time had passed, and after more than a decade locked up in Azkaban, he had not remembered it right away.
"But this spell is really useful." As Kyle spoke, he flicked his wand again, slicing a giant spider that had crept up behind them neatly in half.
"That's still Snivellus's curse," Sirius muttered, still somewhat displeased. "But Kyle, how could he possibly have taught you that?"
"...Was it Kanna?" Sirius asked teasingly.
"Of course not." Kyle shook his head. "I found a book... Well, it was Snape's old Potions textbook from when he was at school. It recorded not only his insights on Potions, but also quite a few spells he invented. Sectumsempra was one of them."
"A Potions textbook..." Sirius froze, then blurted out, "You mean he invented that spell while he was still in school?!"
"That should be right." Kyle nodded. "Sectumsempra was written in the latter half of Advanced Potion-Making. Judging by the progression, it should have been during the first term of seventh year."
"That's impossible..." Sirius sounded even more displeased. "He must have stolen it, that Snivellus..."
"If he really had, do you think Headmaster Dumbledore would have done nothing?"
"Well... um... maybe he fooled Dumbledore."
Sirius kept searching for every possible excuse, refusing to believe that Snape could have invented such a powerful curse as Sectumsempra while he was still in school.
"Sirius, you're not jealous, are you?" Kyle looked at him and suddenly raised an eyebrow.
"Jealous?"
Sirius was like a dog whose tail had been stepped on, instantly jumping to