If "you" refers to all of us, my 2 options for a happy ending are in my posting above :>

Regarding time travel: That's why I hate most time travel stories. Tokyo Revengers does the exact same mistake. The main character jumps between times and only has his own memories from his active experience, yet there MUST be a version of him that experiences all the other stuff, makes important decisions and so on. That's just a massive plothole and I think the authors know that, they're just too lazy to figure out how to do it right. Because you could. It'd just add another facet to the story.

For better or worse, these anime are so shallow ultimately that I don't even care much about these plot holes. If it were Steins;Gate making such mistake, I'd be more upset. But in this generic anime that will be forgotten the very moment the fall season begins? Nah