Hiya! I'm really glad you liked the game so far; thanks for your words and your will to help!
In later stages, the game will indeed have more characters roaming around, side characters as well as some others who will pose an additional challenge for Naoto. Also, the amount of decisions for the player will keep growing, even if it won't be excessive either (but it's true that visual novels lately are becoming more and more poor in that department, and one of my challenges is precisely to correct this). The character customisation issue, though, will be way harder. That kind of option is meant for other game genres; visual novels per se don't focus on including customisation options for their characters, as they are just sprites and little else. I can, though, assure you that in later stages of the game you'll be able to see the characters in various different outfits aside from their typical school uniforms (streetwear, swimsuits, etc.).
Certainly, the progress of the game will be slow since I'm the only one working on it now, including translations, but I'll do my best to keep up the quality that people like you are so kindly mentioning in their comments. And of course, thanks again for your help offer; if I'm in need of ideas or other issues like proofreading and such, I'll be sure to resort to you guys.
Thank you very much and see you!