[@Rin] I'm sure that age is fine. The RP is taking inspiration from both HxH and Dragonball, both series having children even younger than 13 being some of the strongest and/or fastest growing characters. Goku and Gohan being the strongest warriors on the planet at the age of 12 and 11 respectively. Goten and Trunks being arguably as strong as Frieza by the ages of 7 and 8. And Gon and Killua, though not the strongest, are highly skilled fighters with tons of potential at 12 years old. So 13 is probably a safe bet.