It's one of those "sudden exotic GF falls from the sky" reverse isekai stories. Nothing special (I do like the character designs). But to think they actually became lovers quickly and there's none of that "will they won't they" song and dance that's plagued male-oriented romcoms for a long time. That at least is very promising: they're already dating from chapter 1. No more of the usual waffling about confessions and the like. So I will expect them to act like lovers.
From her perspective, she had just finished a very important duty to her world/people and now it seems this time she has decided to live her own life for herself, as she sees fit. But by choosing to fall in love with a human she's setting herself up for lifespan-related heartbreak... She does say she's immature so maybe she's still a young elf by elven standards? Maybe she hasn't actually thought about that heavy stuff yet.
Mildly interesting how there are other elves already (secretly) living in his world. Some of them seem to have reverse isekai'd themselves long before our female lead teleported into this world.
