Ahhhh this is a good one!! I think the most obvious answer would be friends-to-lovers, meeting at school in either high school or university, then eventually just hanging out long enough that they sort of just... realize they're dating. There's no definitive start. 😌 Otherwise, since Gege said Yuuji would be a firefighter in a world with no curses, maybe he saves Megumi from a fire and they end up staying in touch afterwards! Or they connect through a mutual friend, Nobara! Or Megumi is the vet that Yuuji takes his pet to when they get sick. Regardless, I think their connection would be a pretty instant, "love-at-first-sight" type thing!!