Disclaimer: I do not own Katekyo Hitman Reborn, nor do I own any of its related characters, etc.
"Hey, Dame-Tsuna," Reborn said "It's time for training."
"Can't I have a break for once?" Tsuna groaned.
"No." Reborn said in response as he transformed Leon into a gun. "Besides, I have a new bullet I wanted to test." Reborn showed Tsuna the rose-colored bullet before loading it into Leon.
"Do you have any idea what that will do?" Tsuna shouted, but it was too late; Reborn pulled the trigger, the bullet breaking open in midair as it flew at Tsuna's head. A blast of pink energy exploded from it, but striking Tsuna between the eyes, and knocking him unconscious.
"What... what happened?" Tsuna said as he came to. To his surprise, his voice sounded much higher in pitch than before, and his entire body was sore, but he wasn't quite sure why. His room swam before his eyes, and as the world came into focus, he saw Reborn standing in front of him, frowning.
"This was... unexpected." The Arcobaleno said. "Seems this bullet won't be too helpful at all."
"What do you mean?" Tsuna said, sitting up.
"See for yourself." Reborn said, holding a mirror in front of Tsuna. A loud, feminine scream could be heard from miles away as Tsuna saw what had happened.
"Jyuudaime!" Gokudera shouted, bursting into Tsuna's room and looking for any potential threats to his boss.
"That was fast." Reborn remarked as Yamamoto walked in behind Gokudera.
"We were just outside Tsuna's house when he screamed." Yamamoto said, laughing a little. "Gokudera freaked out and ran inside."
"Don't make it sound so pathetic!" Gokudera said. "Anyway, what happened, Jyuuda-" Gokudera stopped speaking abruptly, his eyes fixed on Tsuna. Yamamoto's laughter halted shortly after, and the cheerful expression changed to one of shock to match Gokudera's.
"It's just me, Gokudera-kun, Yamamoto." Tsuna said, blushing a little. "I know it's weird, but-"
"What did you do with Jyuudaime?" Gokudera shouted furiously, pulling out his explosives. "Talk now, or I'll make sure you never leave this room alive!"
"Hey, calm down, Gokudera." Yamamoto said, laughing nervously. "I'm sure Tsuna's fine."
"Tsuna's perfectly fine." Reborn said, smiling. "She was just testing my newest bullet." It was obvious from Reborn's expression that he was going to enjoy this.
"She?" Gokudera said. "But Jyuudaime's a...!" Gokudera's sentence trailed off as it dawned on him that the girl in front of him was indeed Tsuna. "Forgive me, Jyuudaime!" Gokudera said as he bowed down in apology.
Tsuna, indeed, was no longer a boy. The bullet that Reborn had fired had altered Tsuna's gender, and his body matched that. Tsuna's light-brown hair no longer defied gravity, but instead hung slightly past his- or actually, her- shoulders. A faint blush had spread across her cheeks, as she realized how ridiculous she must look. Tsuna's figure was now more slim and delicate.
"So, Tsuna, I guess you can feel free to get hurt now, because at least Doctor Shamal will take care of you." Reborn said, smirking.
"Shut up!" Gokudera said, glaring at Reborn. "This is all your fault! I'm going to kill you for this!"
"Hey, calm down, Gokudera!" Yamamoto said, holding Gokudera back from attacking Reborn. "I'm sure it will go away eventually."
"Hm." Reborn replied. "I'm not sure about that. This bullet was designed to only be reversed by a second bullet, and it took a week to create the first one."
"So I'm stuck like this for a whole week?" Tsuna shouted, a look of horror on his face.
"Not necessarily." Reborn said. "It may be a shorter amount of time, or most likely a much longer one to get a second working bullet."
"No!" Tsuna cried. "What if Kyoko sees me like this?"
"Don't worry, Jyuudaime." Gokudera said. "As your right-hand man, I'll make sure nothing happens!"
"I'll do my best to help, too." Yamamoto said, grinning.
"Thanks, Gokudera-kun, Yamamoto." Tsuna said, sighing in relief.
"I'll have to use this opportunity to test their loyalty to Tsuna." Reborn thought. "And I can always get some enjoyment out of this, too."
"Hey, Tsuna." Reborn said. "Gokudera was thinking that you're the cutest girl he's seen."
"How would you know what he's thinking?" Tsuna said skeptically.
"I can read minds, remember?" Reborn replied, smirking.
"Well, it's probably not true, right Gokudera?" Tsuna said, looking at the spot where Gokudera had been. "Gokudera? Where did he go?"
Author's Note: yeah, short chapter. Next one will be longer. I kinda wanted to see this kind of thing happen in Reborn a while ago, but then I realized I can write a fanfiction about it.