Here are some questions and advice. Hopefully your game development and writing will go well.
First, I didn't find your character sprites to be appealing. But since I'm not good at criticizing art, I'm not entirely sure what you could do to improve them... Maybe someone else can offer suggestions.
Second, I wasn't entirely sure what to make of your story. Is "Hana-chan" a real person, or something different? How much of a role will this character have in your slice of life story?
Third, have you already done some research on ordinary life in current Japan? If not, be sure to do some informal research. At least a few people on this forum can probably help you in this regard.
Fourth, I tend to like BxG harem stories, and I sometimes enjoy fiction set in Japan. But do you have specific reasons for writing a slice of life story about one boy and several girls as romance options? And could your story work in another place or time?
Renji is the protagonist of the game. He's the laziest guy you could find in Prufille High...
I tried searching for the word 'Prufille,' but it does not appear to be a real word. The only coherent search result I found was the name of a street in Florida. Is this a made-up term?
Yuri is the student council vice-president that hates uniforms. She wars the uniform differently, but she’s such a good student she’s accepted in the student council...
In your setting, are school uniforms mandatory? If so, how much can people modify them?
Also, how much power does the student council have? You might want to research this. A lot of what is discussed in the Absurdly Powerful Student Council article
is just fiction, but some of it is based on real life.
4 (maybe more) obtainable girls
Think about the scope of your story. How many romance endings do you want to create? Will there be bad endings or friendship endings? How long will each path be?