The main idea of this story is interesting, but it's not something super original either, since isekai is not an uncommon theme in manga. The pacing, if you read all the chapters together is good.
The world building is a little weird, because when Rei got in, there wasn't magic and there weren't any signs of these element monsters being around. Adding them 8 chapters later feels like the author wasn't sure about how they wanted the world to be from the start. Anyway, the magic part is not bad though.
The overall plot is interesting, but the weak spots are the main character and her (lack of) chemistry with Claire.
I liked that chapter where they were talking about mc's sexuality, because we got a glimpse of how she actually was in real life. This gave her more depth, because other than that, I find her character cartoonish. She's just an idiot and it doesn't make any sense why she likes Claire that much. I mean, it was just a character from a game...I know this is supposed to be for comedic reasons and the only way to make Claire warm up around Rei, but Rei enjoying getting bullied by her is a bit cringey and makes her look like an idiot.
And now we are at the point of getting a development between Claire and Sein lol. I was like, yeah start dating, I don't care. Because the chemistry between Claire and Rei is almost zero. I know it makes sense regarding Claire's character and how she is "destined" to dislike Rei, but so far I don't care much about shipping them. Also I can't say I like Claire much either, because she is behaving like that typical kinda idiot villain too. Other than showing signs that she doesn't want to really bully the mc, she gives off that typical spoiled brat vibe. But I'm sure there will be a development regarding the characters, so I will wait to see my overall opinions until later.
I'm really curious to see if we will get an explanation about why Rei got Isekai'd, if she will reveal it to Claire once they get closer, if she will go back to her world, or even if Claire would go back with her.
These are the main attractions to the story for me right now, and I want to see them getting addressed until the end. I think it will be shallow and a waste of potential otherwise, to just have Rei stay in that world forever and pretend the getting transferred into a game was normal.