@mza I didn't make the visuals for the girls or the background art-- I used [KHmix](http://khmix.sakura.ne.jp/download.shtml) ([link to an english version in this forum thread](https://lemmasoft.renai.us/forums/viewtopic.php?t=15061)) to make the visuals for them.
I got most of my background art from the [Ayaemo Creative Institute website](http://ayaemo.skr.jp/materials.html) (you might want to use google translate if you can't read Japanese-- I can't) or from just doing google image searches.
I made all of the other art myself, such as the top-down shooter tile/character/weapon sprites.