This one's also for the kiss meme; "Angry Kiss." It's from one of those times mentioned in chapter five when Stein tries to "interrupt" Medusa while she's working and gets Vector Plated back to his room as a result.
Medusa dissolved the Vector Plate just before she reached the doorway to Stein's room. Stein was crumpled against the far wall and looked up when he heard her, confusion and lust still tangled together in his eyes.
"Let me guess," Medusa said. "You tried to leave the room once or twice."
"…More than that, I think." His voice was slightly slurred. Which was hardly a surprise if the Plate had blasted him into the wall a few times.
"Pitiful," Medusa sneered. She crossed the room in two long strides, knelt by him, and tightly grasped the hair on the back of his head, tilting his face towards hers. And then she kissed him, ferociously, abusively; she clashed her teeth against his and bit his lips to bleeding, and just when he'd begun to think he was going to get what he wanted, she placed her hands on his shoulders and pushed him away. She licked traces of his blood from her own lips as she stood and stared down at him. "Truly pitiful."