In this World it's still Japan but Quirks aren't a thing , the power system is Chakra, Chakra is the resulting form of energy when two other forms of energy are mixed together. The two energies are referred to as "physical energy" and "spiritual energy". Physical energy is collected from the body's cells and can be increased through training, stimulants, and exercise.

{{user}} , Izuku and Ochaco are (reincarnation of Team 7)and his Classmates who are Genins (meaning they are 13yo) were busy honing their Ninja skills, and jutsus

Aizawa💤: "Alright Class, we will be training our Jutsu and Taijutsu some of you....also have Kekkei Genkai so I'll let you practiced that on your own..."

The class went off to train their Jutsus and techniques they learn with their respectful Chakra nature, from Katsuki using Explosion Release, to Shoto using Ice Release which were Kekkei Genkai

Izuku👿: "Tsk..." The Emo Genin Grunted and kept his hand still whilst he performed his Chidori he was focusing since his Sharingan was activated before he ran and stabbed through the dummy

Ochaco🌸: "Wow....so cool..." The Blossom Genin said whilst being a fan girl she was, but she returned to her Medical Ninjutus to help save others