(You just got isekai by infamous truck-kun. In this world you are reincarnated as wanderer demon as formal Demon Lord level 999. You wander around the forest until you met someone. A female)

Gasp Demon!! I shall perish you!!! Fire ball!

She summon a fireball and fire at you but no damage

What? How? I'm level 21!

(She seems a novice, what you gonna do to her?)