I'm not even gonna nag about Koyuki not having a last name; this precious bean is so underrated it hurts.
Also, I'm sorry about all of the child AU's but I've got this one then a Lawless x Reader where they babysit a Child!Licht after this one then I'll - hopefully - stop with the child AU's for a while, if you guys want me to.
So Child!Reader.
~*~
It was no surprise to anyone that Koyuki was such an amazing big brother.
He was always making sure (f/n) was safe when the two were home alone, he would take her out to the park and round her friends' houses, and would even do the daily school run if his parents were still sleeping or to busy to tend to the young child. The last one would usually make the boy late for school himself, but no one would tell him off because he was just too darn sweet to give a detention to.
People often called Koyuki (f/n)'s "Second Parent" because he was so caring about his little sister.
He would never get mad at her when she broke his things, he was always glad to dress her and help her with her homework and he would even go to her parent's evenings instead of their parents because he himself liked to know where (f/n) was at with her studies.
And when she got too tired to walk home from school or if she ever hurt herself at the park or round a friend's, he would always give her piggybacks home and sometimes stop for ice-cream.
It was clearly evident that Koyuki cared deeply for (f/n), so anyone could've imagined that the day the six-year old girl snuck out of the house under her older brother's watchful eye, Koyuki flipped.
~*~
"(f/n), would you like cheese or ham in your sandwich?" Koyuki called out to his younger sister from the kitchen, where he was preparing lunch for the both of them.
Their parents were away on a two-day course for work, leaving Koyuki to look after (f/n) without warning or anything. But Koyuki didn't mind, he loved looking after (f/n), as it gave them the chance to do stupid shit that brothers and sisters would usually do.
When Koyuki didn't receive a reply from (f/n), he called her name again, and when she didn't reply to that, he stepped out of the kitchen and broke out into a cold sweat when he saw the front door open, and (f/n) nowhere to be seen.
He didn't even think about picking up his phone or a jacket before he was running out of the house, not even closing the front door behind him.
Taking off in a sprint down the road, Koyuki called out (f/n)'s name over and over again, receiving a mix of worried and confused expressions from passersby.
"Koyuki!" Ryusei called out to the boy, and the latter turned around faster than light when he heard his name. "What's going on?"
"(f/n) wandered out of the house and I don't know where she is," Koyuki panted, running a shaky hand through his fluffy brown hair as Ryusei tapped his chin in thought.
"Ok, where are her favourite places to go?" The blonde boy asked and Koyuki thought for a second before clicking his fingers and looking back at Ryusei with realisation in his eyes.
"The park!" He exclaimed, and Ryusei nodded before the two of them continued to sprint down the road until they reached the park.
And sure enough, (f/n) was there, laughing to herself as she went down the same slide over and over again, and Koyuki almost started crying from the sheer sight of his sister safe.
"(f/n)!" He called over to her, and (f/n)'s smile brightened when she saw her big brother with Ryusei.
"Koyuki! Ryu-chan!" She called back to them, waving as she slid down the slide once more before running over to the two.
Koyuki knelt down and gave his sister a big hug when she padded over to the two, not even angry about her leaving the house just minutes before.
"(f/n), why did you leave the house alone?" He asked, still panting as he tried to regain his energy.
"I wanted to go to the park, Koyuki! You said we could go to the park today!" The girl answered, her sweet little voice enough to make the boy crack a smile, and even a chuckle!
"(f/n), I said after lunch we could go to the park," he corrected and (f/n)'s smile faded, replaced with a look of guilt. "What you did was really really bad, and you had your big brother scared for a moment."
(f/n) looked up at Koyuki with her big (eye colour) eyes, and Koyuki couldn't help but smile at how sorry she looked.
"I'm sorry, big brother," she apologised, hugging Koyuki. "I won't do it again."
Koyuki hugged (f/n) back, and Ryusei watched proudly at how his best friend was so good with kids. Quite frankly, Ryusei couldn't stand children.
"I know you won't," Koyuki rubbed her back a little before pulling back and smiling at his little sister. "Now, why don't we go eat lunch and watch (favourite Disney film), ok?"
(f/n) nodded happily and Koyuki stood up straight, holding his hand out to (f/n) as Ryusei held out his hand for her too. (f/n) was about the only child Ryusei could actually tolerate.
The three of them walked home peacefully, and Koyuki thanked Ryusei for keeping a clear mind in his moment of panic, to which Ryusei replied with a "my pleasure" before leaving.
Which left Koyuki and (f/n) to eat lots of sweets and watch a load of Disney movies until they both fell asleep on the couch, (f/n) laying on-top of her brother which was a sight for sore eyes when their parents came home later that night.
~*~
Hope you guys had an amazing Valentines Day!

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{completed} one-shots 》servamp x reader
Fanfiction//requests; closed// ‼️‼️‼️ a collection of (shitty) servamp x reader one-shots brought to you by yours truly ^-^ ‼️‼️‼️ i write: fluff, angst, songfics, headcanons, literally anything but lemons. ‼️‼️‼️ {i do not own servamp or any of its character...