Nice work on this visual novel concept! some of the things I would consider maybe would be how busy your floor tiles seem to get within the classroom. Its not to distracting and I see your trying to go with that wood texture, it just feels extremely busy. this makes the rest of the characters look a bit odd with the way they blend in.
Also for long visual novel games consider adding a mute button for the music but adding some sound effects for the text continuation. some little soft jingle or whatever to give that feedback of the player doing something.