Lux in Tenebris

Lee Chan has six months left to live. His body is failing, his fellow hunters see him as a liability, and the only thing he has left is the ghost of his own talent. He refuses to die in a hospital bed, hollow and alone.

Choi Seungcheol has been alive for four centuries. He has outlived lovers, friends, and enemies. He has buried everyone he ever cared about. He lives in an isolated castle, speaks to no one, and has convinced himself that solitude is preferable to loss.

When Chan breaks into Seungcheol's castle with a grenade and a desperate demand - turn me into a vampire, or let me die trying - Seungcheol laughs in his face and throws him out. But loneliness recognises loneliness. And Seungcheol has never been good at walking away from things that amuse him.

[Cross-posted on AO3 under the same username]