if the boy here really love her I think the best one is to avoid her before the elf fall in love with the boy, here in this manga the first one to fall in love is the boy so if he avoid or at least don't let the elf to fall in love with him is how he truly love her, imagine live for another hindred of years alone.... obviously he doesn't want that right? Then the best choice for him is just let go of his love....and no you got the wrong point, dying together or suicide is not my point what my point is the difference in lifetime between them, also well if he surely can make his lifetime at least similar to the elf then go on... But well I don't want to debate any longer for a fictional character, I'm sorry if I inconvenience you in anyway, I apologise.