Yeah that is part of my concern. You don't know what has happened over the 10 years, whether with the world or with the LI's. I mean some of the LI's barely got to know the MC, it would be understandable for them to simply move on with their lives and find partners. But while it is understandable, it would suck for the player and the MC lol. And that was the other point I tried to make when I brought up the LIs, which was just what you said. We just got to know them for the most part, and then we get hit with a 10 year jump, now we have to get to know them all over again. The time jump this early would just seem to make the story convoluted.
I mean it would work if we could follow the girls and see what happens, see how MC's death impacts them, but since we are following MC, we aren't going to be privy to any of the growth or events until an exposition dump. Well I assume. Which the only one with a major connection to MC is Yua, everyone else would just say "sucks he died" and move on . And is MC just gonna be his 20 year old self while everyone else is in their 30s, as you said? Eh Gotta stop speculating and just wait...
That is where my thoughts went when I learned of the time jump but ultimately I don't know how the dev is gonna go about it so it doesn't make much sense to speculate. They might undo the 10 years, might go back and stop the attack, or might just pick up 10 years later and continue the story from there, idk lol will find out though.