Hello there! I don't really have much to say to this One-Shot, though there is a piece of information at the end. Enjoy.
(Honestly, I sometimes don't get how some people can write entire paragraphs about the story etc. before they start with the story. I don't think it's a bad things. It's just that I'm not able to do that, but wish I could do it sometimes _^_ Anyway. Enough of my blabbering.)

Pairing: F27

Warnings: F27; Fem!Tsuna; Shonen-ai; no beta-reader

Key:
'Chinese'
'Normal (Japanese)'

It was almost midnight. The mansion was bathed in darkness as most of its occupants were asleep. Except for one. A single room was lit by a small light, which was enough to illuminate the office desk. Numerous stacks of documents were piled on the desk. Here and there a book peered from between the documents.
The scratching of a pen could be heard, a delicate hand leading it. Tsuna let out a sigh as she continued with her report of her last mission. She really hadn't thought she would spend the night of her twentieth birthday writing a report. Then again, the mission had been a long one. She just wanted to get it done.
The brunette wore a smile of nostalgia as she remembered the last time Reborn had to threaten her for her to pull an all-nighter. It hadn't happened in almost two years. It was like a switch had been turned on after her eighteenth birthday, a year after taking up the position of the Vongola boss. She hadn't changed overnight, but she had gradually lost her clumsiness, shyness and other traits that made her Dame-Tsuna. She still was clumsy and shy in some moments, but they had become extremely rare.

The clock struck midnight when a tray was placed in front of the brunette. Tsuna was too tired to actually be shocked. The fragrance of an unknown tea assaulted her nose. She put the pen aside and lifted her head to see who else was up around this time.
Fon, the Storm Arcobaleno, was sitting next to the tray, which held two Chinese tea cups and a teapot, steam rising from its opening. His small smile was present as always. Tsuna blinked in surprise wondering what the infant could be doing in her office at such an hour. As if sensing her wondering, Fon gave her an answer almost immediately.
'Happy Birthday, Tsunayoshi', Fon said, his smile transforming into one that was only reserved for Tsuna, though the brunette didn't know that. Tsuna stared for a moment before a smile made its way onto her face.
'Xiexie, Fon-san', Tsuna replied with an incline of her head. Fon poured tea into both cups and handed one to the woman, who gratefully took the tea. She took a careful sip and sighed contently as the hot liquid flowed down her throat. She liked the taste of the tea.
'Why are you awake at this time, Fon-san?' Tsuna asked setting down the cup. She was truly curious about it, since she rarely encountered anyone at night, especially in her own office.
'You seemed distressed when you came back from the mission and decided to cheer you up by being the first one to wish you a happy birthday', Fon answered while sipping his own tea. The answer brought another smile to Tsuna's face.

In moments like these, Tsuna was glad how things had turned out. At first she had only lived with her Guardians and Reborn in this mansion. However, after a while the Arcobaleno decided to live with them one after another. First Colonello and Lal, then Aria with her daughter Yuni. Even Verde and Skull had come to the mansion after a while. She suspected it was Reborn's doing.
Somewhere along the line, Nono had decided that Varia had to live with them, too, and with them Viper. She remembered the first few months after they had moved in. She had to suppress a wince while remembering the many injuries she had to treat back then. It had taken one of Tsuna's very rare death threats for them to get along at least well enough to not jump each other's throats.
Tsuna wasn't sure when Fon had moved in with them. He had started to visit regularly pretty soon after Tsuna and her Guardians had moved in. At first he had visited once a month, but the visits had become for frequent over time. By the time Tsuna had been eighteen, Fon had been visiting once a week and six months later the visits were almost daily and he often stayed a night or two. From then on his stays had become longer until one day he just didn't leave anymore unless he had to for a mission or personal business.

Tsuna returned to reality and put down her cup, resuming writing her report. Fon sat in silence watching the brunette finish her work. After almost an hour, she was done. She put the report into a spot where it would be noticed right away.
'Good night, Fon-san', Tsuna said as she rose from her seat. Fon watched as she walked towards the door, observing her movements carefully. He knew that she was tired and was afraid that she wouldn't make it back to her room. He was right. Just when she passed the couch, she collapsed to the side and onto the couch her lower body hanging off the couch.
Fon jumped down from the desk and walked over to her. With some difficulty, he managed to get her onto the couch completely. Then he vanished from the room for a few minutes and came back with a pillow and thin blankets. The Arcobaleno jumped onto the back of the couch and draped the blankets over the brunette's sleeping form. Next he lifted up her head gently, placed the pillow beneath and lowered her head back down onto it.
'Sleep well, Tsuna', Fon whispered and placed a gentle kiss on Tsuna's cheek. She didn't even make the slightest movement, further proving Fon's suspicion. The mission must have been really hard. He let a small sigh escape as he thought of the reason why Reborn had sent her on that mission.
The Storm Arcobaleno hoped down from the couch and retrieved the tray with the tea set. He switched off the light, causing the only remaining light source to be the floor light shining through the crack of the open door. He walked towards the door, stopping in the door frame. Fon glanced at the Vongola Boss one last time, a smile tucking at his lips, before leaving the room and closing the door.

Now the info I promised earlier:

For now this is only a One-Shot. I plan on turning it into a multi-chaptered story one day. That means that the title might change once I can get to turn this into a multi-chaptered story. Until then this story will be marked as completed. What I can already tell you, is that Fon is going to court Tsuna. If you have any wishes or suggestions, please feel free to tell me.

Reviews are always welcome ^^ Hope you enjoyed.