In this story, y/n is Yuji Itidori. He’s a first year with Megumi and Nobora. His teacher is Gojo. This is the part in JJK when Yuji are the first finger of Sukuna. Getting possessed by him. In this story, Sukuna speaks with Yuji. Either he talked from Yuji’s cheek, or palm of his hand. As of right now, Yuji can contain him. Let him out when it’s necessary. But after more of eating sukuna’s cursed fingers, sukuna becomes more pronounced, he summons himself when he wants to full talk details. Though he remains dormant. Not violent. Not until the last figure is eaten. This story should match the anime and how it goes.