A crossover between KHR and Harry Potter because I can't resist doing it! There's some changes here and there so I hope you guys enjoyed it!
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"Woah! This place is huge!!" shouted a fifteen year old Lambo as he looked around, amazed at the big structures.

"Of course it's big. It's a castle." said Gokudera behind him.

"It must've looked very pretty a long time ago, before it was abandoned. I wonder how it looks like..." I-pin wondered.

Yamamoto whistled as he looked up, noticing how high the ceiling was. "Must be hard to keep this place clean."

Both Mukuro and Chrome entered the hall where the others were gathered, Hibari silently following behind. "Kufufu, I won't be surprised if there are some hidden traps here." Mukuro commented with a sly grin.

"Mukuro, please don't." Tsuna warned. "And everyone, please stay close together. I don't want anyone to get lost in this place." he added.

Reborn -perched on Tsuna's head, just nod his head in satisfaction as he watched his student lead his Family into the ruins.

"What are we even looking for, Reborn?" Tsuna asked while navigating his way through the abandoned castle.

"A mirror, said to be able to show your deepest desires." Reborn supplied. "It's known as the Mirror of Erised."

Tsuna just hummed, half-curious and half-doubtful about this. Nevertheless, he continued his way through until he came across an iron double-door.

With little hesitation, Tsuna pushed those doors open, revealing a room full of worn cupboards, furnitures and other old stuff.

"Well, if we're trying to find a mirror, I'm guessing this sort of place would be a good place to start," Tsuna sighed.

With that said, the others split up and began to search amongst the old pieces for anything that would look like the Mirror Of Erised.

While Tsuna was looking around, a glint of light behind an old chair caught his eyes. Walking around it, Tsuna found himself standing face-to-face with a full-body length mirror covered in dust and cobwebs.

Holding his breath in, he dusted off those dust and cobwebs, coughing a little in the process. Once he was done, he looked into the mirror with Reborn now standing at his side. "Is this the mirror, Reborn?" Tsuna asked.

Reborn didn't answer as he stared at the image formed within the mirror. A man with curly sideburns, wearing a black suit and a black fedora with yellow-stripped band on his head was staring back at him, a smirk settling on his face.

Tsuna just looked questioningly at Reborn before he looked back at the mirror. The only thing he could see was him and Reborn, staring at the mirror, and his Family, scouring through the pile while fighting, making the place even more messier. Groaning, Tsuna left the mirror and head towards his Family, stopping them from killing each other and scolding them for making the mess.

Reborn stared at his original form a second longer before he tipped his fedora down, shielding his eyes from the image. With a soft sigh, he walked away from the mirror and joined into the fray, his lips pulled into a smirk when he heard Tsuna cry out in frustration.

His deepest desire may be to have his original body back, but for now, Reborn is content to be around his student and his Family.