So just as I predicted, they did end up having one last (and first) tryst as a way of consummating their childhood's first loves. And I assume that Reiji was born from this union.
This is so sad man. They still had so much love for each other. I blame Esemori because he didn't have it in him to protect her. He should've trained to become a stronger version of himself, so that he could go out with such a sought-after girl with high status, while being able to fend off the malicious actors who would inevitably be drawn to her. I know it's not easy, but sometimes, that's your responsibility as a man - to protect your woman by any means necessary.