First thing he thinks of when all enemies respawn at once: "What's the most efficient way to grind this?" Powergamer mindset.
He asks why he never used it before, but the way he worded it was like he just became capable of using it. Something lost in translation?
Kind of strange that you need a lot of power to ignite the gas. Generally you just need to start those reactions with far less energy. This seems like they used as much energy is it would take to blast them all with magic, or something like that.
Elixir GET!
And now they have their grinding plan in action.
Birb Dragon.
How to make an OP mc
1. Give them an xp glitch
2. Good job, you've got your OP mc
And that's already twice as many steps as your average OP isekai MC!