I quite like this. The main couple are a super rarity these days, in that their personalities actually make sense. Both of them are reincarnated versions of their prior selves, and it really shows. The female lead (now human) used to be a 200 year old Elf Sage, and her personality is a great mix of socially awkward because she used to be revered as the sage and didn't actually have real relationships, and yet still girlish and giddy about her first love, now that she's on the same side as the MC. The MC, now an 18, yet formerly a 70+ year old Hero (commoner both times), is both laid back and mature (he's ACTUALLY 90!), and yet has his quirks (again, due to being a hero for decades upon decades). He's also quite devoted and happy with being with the Sage, because while they may not have been married, back in the past they were absolutely the most important person for each other.
Honestly I adore the concept, and the first chapter(s, it's split) is great. The plot takes entirely in the present, and seems to be fairly standard magic-school-fantasy, but with the setting of those two, and a bit of mystery of what happened in the last 1k years. For example, the Hero is ONLY remembered by the word-of-mouth Elves, and no history records him or even his country (which makes no sense, as the 'enemy nation - the sage's' is the current country.) So figuring out why history seems to be intentionally erased is the current plot.
But frankly, I'm not to worried about it. It's not super amazing, nor is it lame as hell. Most of the story just has some comedy, SOL, and cute romance. The two main characters are stupidly OP, both in the past and in the present. Makes for a great set up. It's one of those manga where you just squee 'JUST GET MARRIED ALREADYYYYY!!!!" ... oh yeah, they're engaged!
Cute, and worth a read, but don't expect anything amazing. The only thing that's flat out amazing IMO is the first chapter, which is really well done.