Or maybe something really messed up happened to him or he committed a taboo to the point that they had to erase his existence completely
no seriously theres so many possibilities and the mc chose to say
"nah you dreamt it, its fake"
It's weird that he said that since he saw that vision of kim seoho
Bro really said "yeah that person you thought about for 1500 years? A figment of your imagination"
NO THAT PISSES ME OFF SO MUCH
Maybe his past lover used a fake name? No one ever considered that?
Or maybe he wasn't a human? The register only has names of humans who have lived right?