That's gonna be a sad romance, because we know sensei have long journey and mc just a normal human
Depends on how you look at it, honestly. And how the author writes it.
Sometimes, yes, it's a "I've buried someone again... 😩" type deal. Sometimes, it's a "It's okay, I'm following you
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" type deal. Sometimes, it's a "Ahhh, did you enjoy the time we had together? Me too, love. I'll see you when I see you..." type deal.
There's other types out there, but it doesn't always have to be sad. Hell, I saw an elf semi-recently who had several wives, some of which were, like, 70. And he loves them all.
Long lived: Potentially the harem protagonists we want...