The overall idea is alright but a lot of it seems pointless too.
This is one of those fanfics where the mc feels like +1 that is supposedly the main character but doesnt really change the main plot.
For example she knows the plot but keeps Shido alive.
Another thing that I don't like is hoe she just conjures whatevrr she wants from soundless pistols to soundless grenades out of thin air...
The overall character herself is likable enough, I just don't see much value in her bring part of the story if she doesn't drastically alter events like Shido getting on the bus when she catches him red handed and saves his would be victem.
Its like those harry potter novels where there is this 4th member of the golden trio who uses the plot to seem smart but doesnt change a damned thing worth mentioning.
So yeah. I like the mission style entry into the world, I like the personality of the character, but i don't like the fact she conjures things out of thin air with no logical reason for it nor leaves Shido behind when theres ample reason and chance to never have him reach the bus in the first place.
All in all the story does have potential.