A little amusing, but it really shows how standards have changed.
Also, definitely Euclid.
Here's the "Common Sense" ranking which most people have been using since the site evolved past its original few hundred articles:
Safe - It's just a thing. It's a weird thing, but you can store it and...
I hate to be a reductionist but... buy some guns. Even villagers can be easily trained to use modern ones and even if they get stolen they can't be replocated and he controls the supply of ammo. Wipe out those 200 cavalry with no survivors and no one even has to know that you did it with...
"Not gonna tell you who I am~!"
Oh no, if only you weren't one of, at most, a couple dozen students on this trip... and had really recognizable hair... and was probably the only one with a snake.
Wait, it's been a long time, but this one was also an isekai, right?
Do the floaty colorful soul people know about that? Does she have two souls in her body or three?