A certain regular visitor.

Natsu casually entered Lucy's home through the window, which had been left open to allow a breeze in. "You do realize she's going to hit you again, right?" Happy chuckled as he flew in behind Natsu.

"I still don't see what the big issue is... What's the problem with wanting to hang out with a friend every now and then?" Natsu asked with a shrug as he walked towards where the living room of her place was.

"I think it might be the part where you were not invited?" Happy mused aloud, putting a paw on his chin as if that was genuinely in quiestion.

Natsu, having been raised by a dragon, and thus, not fully grasping certain social concepts, simply tilted his head. "Why would she not want to invite her friends in?" he wondered, finding the concept of privacy to be a difficult one to grasp.

Happy just shrugged. "Don't ask me, I don't get it either!" the cat replied.

Natsu shrugged and sniffed the air, before pausing and taking another whiff. "What's that smell?" he wondered aloud. There was something magical in nature, but also... foreign. Almost alien actually.

"You smell something dangerous?" Happy inquired, looking up at Natsu and slightly on guard.

"...I... don't know. It's just something a little off," Natsu replied. He headed towards Lucy's bedroom and opened the door. "...Lucy's not here," he then proceeded to state the obvious.

"Aye!" Happy noted, looking around. Natsu proceeded to continue to use his enhanced olfactory senses to assess the situation. It was odd. Lucy didn't normally leave the house quite this early. And judging from the scent in the air, she had yet to even leave the bedroom today. His gaze then fell on something glinting on Lucy's bed.

"What's this?" he muttered, picking it up. It had a strong scent of that foreign magic on it... and also Lucy's scent. He looked over the golden object carefully and suspiciously.

(I'm rereading Fairy Tail, so my update rate on this one will depend a bit on how much progress I make.)