It feels like a stupid question: how can I save my game? I just started the game and use autosave, but there must be an option to use a savefile sometimes.

Thanks, I never thought about the option to right click. It's my first visual novel. ^^''

It’s actually abnormal in this regard. I haven’t played many VNs either, but usually a visual novel will either have shortcuts to save right on the text box, or there will be a menu you can access by pressing a button such as ESC.