Hunter x Hunter Fan-fiction, New Girl

Akari Fujino is a genius and an inventor. At the age of three she had memorised the periodic table and learnt how to take apart and put back together a clock.
At the age of four she was sent away to a private tutor, Zeno Zoldyck, who gave her a workshop to practice her engineering in. There she lived until she was ten, as her home village didn't have the tools to nourish her prodigy.
At the age of twelve, Killua Zoldyck rebelled against his family and took the Hunter Exam, and ten-year-old Akari asked Zeno if she could join him. Zeno gave his permission, and Akari joined Killua in taking the Hunter Exam.