not visual novels but ive done a lot of acting and written and directed a few films.
if you're just starting out, the best place to start is with what you know. that way you have intimate knowledge of what you're trying to get across. then try to fit this into a three act structure.
yes the three act structure is a little basic but if you aren't super comfortable with writing yet, it super natural because most of what you've seen or read has had a 3 act structure.
then once you get started, let the characters go unless you have a very specific wonderful ending and beginning that just has to be there, then the challenge is how do you get from point a to point b with the middle being as interesting.
i hope this helped! have fun!