Count them, there's 6 feet visible in that first panel. Poison/zombie ladies feet are one in front of the other so you only see blurry toes of the other foot, but carefully counting them still 6 in total. Brigids legs are shorter than MC and again, if you know to look for it her cape is quite...
A God, omnipotent and omniscient - that is all powerful and all knowing, wouldn't make mistakes or get into accidents therefore the only remaining answer is that it's all a part of a greater plan.
It's the art student. The spider is probably eating the neighborhoods cats and dogs or something. But doesn't mind a freebie, so when it comes across the victims bodies it's a free buffet basically.
The friend went missing and died after suspecting the art student and going to visit him.
I thought that was obvious already. Multiple of the past few chapters now had been hinting at it every time we were shown their party traveling towards the fortress.
I bet it was Darth Ahegao who killed the sweety Ageha the first time around because she doesn't want anyone else other than her to be loved by MC not even the other her. Heck, she probably set up the events for the MC's childhood friend to get killed too.
https://www.dndbeyond.com/monsters/16817-bugbear
https://dmdave.com/bugbears-1/
Because they are bugeyed furry men that vaguely resemble a bear. Less so now than in the original illustration by Wizards of the Coast.
Could just be translation error. Or not. We'll find out. There no chance this is a one off character. We'll see them again at some point. Foreshadowing and all that.
edit: OK so based on the comment above Shin is just confused.
The smell of thowup would be very obvious as soon as the door was opened, plus she was demanding for a change of clothes, which works as an additional context clue.