Despite many "perspective views" from the 1st episode being that of the spider, this flashback from Kumoko directly contradicts that:
https://i.imgur.com/VeQSuXO.jpg
So unless this was actually wrong, and Kumoko in fact shouldn't be remembering herself going home to play video games, we can say that Kumoko was a person. She commented on things like wanting to eat rice etc before. A spider going into a backpack every day to school/home is
possible, but a bit of a stretch unless the human somehow allowed it.