AN: I feel like Ciel and Oz is probably one of the best crossover pairings and it's quite a shame how there's not that many of them. This story has always been bugging me from the back of my head and it feels great to have finally written some of it. I have only watched the anime of Pandora Hearts and Black Butler I and II (and I've read some of the manga of Black Butler) so it's mostly based off the characters of the anime. Please Enjoy!

Ch. 1: Where there is light, there are shadows.

"What are you talking about Sebastian? He's been missing for 10 years. I don't think he would just come back so abruptly. And you're telling me he hasn't aged a bit? This is complete nonsense."

Ciel Phantomhive was stirring his morning Earl Grey as his butler, Sebastian, was informing him about the rumors of Oz Vessalius' return. The Vessalius family once had close ties with the Phantomhives until 10 years ago when their heir, Oz Vessalius, had suddenly disappeared. There were a lot of conspiracies to his disappearance and the public even saw the Phantomhives as suspects because of the competition between the Funtom Co. and the Vessalius' business. The tension between the Phantomhives and Vessalius were forever severed due to these rumors, and when the original Phantomhive estate was burned down the Vessalius family was on the suspect list for a certain period of time.

Ciel walked towards his estate's library to find some old photo albums stored away. He opened one dated 10 years ago, when Ciel was still a toddler. He picked up a picture of the Phantomhive and Vessalius family at an outdoor picnic, he assumed the blonde boy with emerald eyes was Oz Vessalius from what little he could remember from that day.

Ciel was searching the photo album to also come across a picture of his parents trying to help Ciel walk around the park. The glimpse of his parents' smiling faces brought a sharp pain to Ciel's chest, but before quickly closing the album, Ciel took one of the pictures of Oz out of the album and placed it back on the shelf. Sebastian smirked at his master's instant reaction.

"My lord, would you like me to send a letter to the Vessalius estate to ask for—", but before Sebastian could finish his sentence Ciel had grabbed his coat and was headed towards the door.

"Sebastian, get the carriage. I must see this for myself."

Sebastian nodded in obedience and went to grab the carriage. Ciel intently stared at the picture of Oz in his hand, so many thoughts were shrouding his mind.

There has to be an explanation to this. People don't just disappear and come back without a reason. The Vessalius's are hiding something and it's the only lead I have right now.