Mira is going to an underground base where everyone is trained, it is filled with equipment they made to withstand their powers. Weapons and armor that can hold against their flames, and alot of battle dummies that are almost unbreakable. The battle dummies are reworked for each generation and im sure you know why, and if you don't just think back to the battle.
As Mira goes to the battle school she sees her students, who she'll be teaching for the next three months. In this batch of students there are only boys no girls, girls are trained a few months earlier or later depending their birthday kids born around the same time are trained together. these cute little boys will lose some innocence in this three months.
As she walks to her students she tells them that the next three months will be brutal with running, fighting basics and that this will build character. Next she takes them to a half mile track they are run around the track twice. This is see how their endurance and stamina so she can adjust their training when or if needed. Why train them this way well why not.
There are ten kids in this group and for the next three months there will be training to build stamina, reflexes and strategies. She starts with endurance and stamina by having them run, do jumping jack, push ups etc every day for a month.
the next month focuses on fighting basics she has them stand in her stance, with arms in front of them with slightly bent knees, and have them practice swings and kicks. If you swing your sword one way then you kick the other way. They do this for half a month the next half month they practice finding flaws in her attacking pattern, and breaking her form. By the time she's finished teaching them the basics she has them fight each other before she leaves.
Since there's ten kids that means that they are fighting in five groups of two. As they are putting into practice what they learned they are somewhat clumsy. The battles are what you'd expect from first timers, and this battle tourney continues for the final month.
After finishing this training course Mira decides to return home leisurely, and maybe sight see to see how much the world changed. After she trains Casa.