From what I understand, this game was originally for the PSP (Vita?), so it's just a port to Steam. That said, it's obvious they put zero effort into thinking about how people actually play the game or bother to playtest it themselves.

With this setup, you might still find the mouse helpful, but it's perfectly playable with just your keyboard hand, which I know some of you "multi-taskers" will appreciate... That said, this isn't a big, fancy guide. Just a quality of life increase over the default. Enjoy.