Very strong start!
Writing quality - epic.
Story Development - I only saw two chaps and they were mostly setup chaps, so I can't say much!
World Background - Patiently awaiting the Grand Appearance of Truck-kun! Actually, wait. She's prob just gonna whoosh through a portal with the two boys and maybe her sister.
Character Design - I have a few problems here and they also tie into the storytelling aspect. But these are mostly just personal preferences so please don't take me too srsly.
The way you write the details of the story are lit. The smells, the sounds, the sights, and the feelings. Most stories tend to only focus on feelings and sight, so I'm super impressed.
But I found myself wanting to skim past these descriptions, because from the first six paragraphs of the story, you told me that the MC is just an averagely interesting person. So when I see her describing stuff, especially everyday stuff like how her apartment looks like and what she does daily, I just automatically think they're going to be something mundane.
And I read the paragraphs fully and sure enough, they're mundane stuff. She talks about how her home looks, a rather small apartment complex for students; she mentions her parents and gets back to diligently praising her sister; then she talks about going to shop once a month...
And at this point, you start to lose me. But after that, she starts to chat with her sister, which let's get honest here, is the best part about the story so far, so I get interested again.
But, when they separate at school and MC starts to think about the average things, you start to lose me again with her average girl perspective.
But then you redeem it by adding that epic description of the manga volumes shaped like a sword. It was a bit hard to visualize, but it was veeery, very interesting. For me, unique stuff like these are much more interesting to read, compared to a beautiful description of a scenery or whatever.
Okay, I think you get my point. But how do you fix this?
Me, personally, I'd add a twist to her average persona. Here's an example.
"I'm just an average schoolgirl with average looks and average charisma, but my hobby is to trap and kill rats."
And then I'd describe her doing average stuff, but doing her best to avoid the rat traps she placed all around her house, and her sister going like, "Momoko! Stop putting rat traps all over the place!"
When they're walking towards their school, I'd maybe describe her glancing around the surroundings, wondering where she would find a rat to trap and kill.
At this point, the reader will prob go wtf. But they'll still diligently read these descriptions of her everyday life, trying to understand what's going on.
She said she's an average girl, but what kind of average girl goes around killing rats? Is she psycho? Or is it normal to have a hobby of killing rats in this world, considering how her sister seemed to take it so casually?
Obviously, this is a super hyperbolic example. And you actually have this kind of twist where the MC loves manga and novels. But let's be honest. Everyone on this website loves manga and light novels. Her loving these things is not a unique trait for your intended readers.
Okay, I went on too big of a tangent here. Basically, I just want you to make your MC more notable, I guess.
But of course, please don't take me too seriously, as this is all my personal opinions.
