After Once in a Lifetime I thought it would be pretty hard to surpass that level of perfection with a free visual novel and with eternum you managed to do just that, the story is just as immersive and the visuals are even better.
Only suggestion for future creations I have is to give the player a choise between multiple MC models, I get that you would probably need to have a lot more funding to be able to pull something like that off since all scenes which include the MC model must be rendered multiple times to make this possible but I still think it would make the games way more immersive.
I myself for example think the MC in eternum looks a little too childish and immature to really immerse and define with the main character and for others this may be other details like for example hair color.
Other feedback would include that in early version walkthroughs it would be nice if you could add a little more details around choises that currently have no effect but might have an effect on later versions or at least mention the best choise already.
Hope you find this feedback helpfull in any way and keep up the good work :)