I can't believe it took this long for somebody to make a promising isekai adult visual novel and thank God it's Caribdis on the wheel. Still holding my review until at least 0.3 but so far here's my short notes:
More Eternum stuff and less college & house sheananigans please. That Eternum thingy is awesome and a great tool for world-building, it feels really unique. But then it's being sandwiched by cliches out of 2017 incest AVN. I know you gotta build sexual tension between MC and the girls but I'm sure you can think of scenes more creative than having your totally-not-mom going to your room and find you naked.
Other than that, this looks very promising. Everything about Eternum itself is intriguing. Goodluck dev!