If I remember correctly it doesn't stick around so keep reading (I really love the story!). As to why they exist, I'm pretty sure it's because the one who translated the sentences was trying to stay true to the original Japanese text or wasn't sure if that was what the Japanese text pointed at. To my understanding, in Japanese you often leave out the subject/object or doer of the sentences and leave it up to context. That is to say that the things in the parentheses are not actually said in the original text, but that way it doesn't make much sense in English, so the translator opted for some kind of middle ground to maintain some originality of the text. At least in the beginning of the story.
Ah, okay. Thanks for responding.
I’ve made it maybe half way through chapter 4, but why are there a bunch of random words in the speech bubbles in parentheses??? It doesn’t make seance for them to be in parentheses most of the time and it’s honestly really annoying. Does that stick around?