So I'm a Spider, So What?, Vol. 1

The protagonist, having apparently died in some supernatural event while sitting in Classical Literature class, wakes to find herself trapped in an egg. Freeing herself, she learns that she is a spider, and soon she finds that she is in a fantasy world, with levels and skills and all the trappings of an RPG.

So she does the natural thing, and exploits the system as much as possible in order to grow stronger–the weak, she has seen, are doomed to be eaten.

Interspersed with the spider's story is the story are scenes featuring Shunsuke Yamada, who has been reborn as Schlain Zagan Analeit, called Shun, and Kanata Ooshima, who has been reborn as Karnatia Seri Anabald, called Katia. The former is a prince and the latter the daughter of a duke. These scenes are set a decade or so in, while the spider's scenes begin, one assumes, begin as soon as everyone is reborn (since she starts by breaking out of an egg). Anyway, there's a time gap.

At this time, the Demon Lord's army is preparing to attack. Shun's brother Julius is the hero, so he should be instrumental in the war.

This volume covers through the end of Chapter 14-4 of the manga.