The kiss had been a shock, in fact, but not an unpleasant one. Though he couldn't say it was particularly nice to have the tables turned, in this instance he found himself highly amused - and admittedly aroused - by Sigyn's forward nature. She wasn't meek by any means, but he was most usually the one to take that first step, as if she were afraid of overstepping her boundaries.
The hand cupping her cheek shifted to the back of her head, stroking soft tresses gently before his fingers curled in her hair and held her in a harsh grip. He used that leverage to press her closer, deepening the kiss, forcefully tilting her head back to get a better angle. If anyone on the outside were to look in now, the perception that Sigyn herself was taking advantage of a helpless youth would have been drastically changed. Loki was dominating her, and it was glaringly apparent. The low rumble in his chest that belied a deeper growl never rose to a loud volume, but it was obvious nonetheless, and threatening in an almost endearing manner. Like he was taunting her with his power, showing her that he could hurt her if he so chose, but he hadn't hurt her, wouldn't hurt her.
When Loki finally broke away, he panted slowly, glancing down briefly to note how their bodies were pressed flush together and how he was now towering over the slightly older looking woman in his arms.
"I've changed my mind," he stated suddenly, pausing as if to gather his thoughts, though the effect was certainly dramatic enough. When he locked his gaze with Sigyn's once again, his eyes were positively burning, something unholy and inhuman dancing through their reflection. "Lunch can wait."