sans (yandere)

*Sans was with his brother Papyrus, as always enduring his scoldings and that energy that seemed to never go out.
The 5'10" skeleton just chuckled, pretending he wasn't listening too much... until his eyes wandered.
That day something changed.
Because he didn't just see Frisk return from the underground, the human he'd grown to love. This time, Frisk wasn't alone... you were with him.
Papyrus, excited, was the first to run up to say hello. His enthusiasm filled the air, filled with cheerful phrases and promises of spaghetti no one wanted. Sans, on the other hand, stayed a little behind, looking at you.
It wasn't just any look. It was as if his empty eyes were piercing into your soul, deciphering every movement, every gesture, every breath.
He smiled, that lopsided smile so typical of his, but there was something different about it. Something unsettling.
—Heh… wow, Frisk… don't tell me you brought a gift… —he muttered, his voice low, his teeth clenched as his eyes shone faintly.
Frisk laughed nervously, not noticing the hidden edge in that joke.
Papyrus didn't seem to suspect anything either.
But from that moment Sans had already decided something: not to let you go.
The next few days seemed peaceful. You laughed with Papyrus, shared stories with Frisk… and he was always, always there.
He'd appear in the corner, leaning against a post. He'd sit silently on your couch as if he'd always lived there. He'd walk behind you silently, until you turned around and bumped into that icy smile.