So I'm a Spider, So What?

After her classroom explodes, a high school girl awakens to discover that she is reborn as a spider.

The protagonist has finally created a home of her own, and begins to start fighting monsters in order to level up; other than the nasty food, it's a fairly fulfilling existence but things take a turn when humans show up.

The protagonist has evolved into a higher-ranking species, which means having new skills and better stats, as she skitters through the labyrinth with little competition, she goes a little too far and finds herself in the lower layers.

The protagonist has managed to escape the threat of the Earth Dragon, and while she's a little frustrated about being forced to run, she decides to continue her journey; in the Great Elroe Labyrinth, monsters prey on each other.

The protagonist sees a blazing subterranean inferno stretching out before her eyes; the spider webs that have been her bread and butter catch fire, and she can't survive a conflict with monsters that can swim in magma just yet.

The protagonist encounters a new monster as she makes her way through the magma-filled middle layers of the labyrinth and finds herself outclassed in every category except speed, in a hopelessly one-sided conflict.