This is a summary based on our understanding of the series.
Please also note that this summary contains spoilers.
Also known as: Guardian: The Lonely and Great God or The Lonely Shining God – Goblin.
Goblin (Kim Shin) made miracles and Ji Eun-tak was one of them, who later on turned out to be his bride.
Eun-tak is the only one who can pull out the sword and who can end the Goblin’s immortality. Kim Shin discovered people who are also reincarnated; it includes Sunny (Kim Sun), his sister, who fell in love with the Grim Reaper.
When Eun-tak pulled the sword out (unknowingly) , Kim Shin was erased from all their memories. He was gone and then came back when Eun-tak blew a candle.
They stayed together when he came back but Eun-tak died in a car accident. Since it was her first life, Kim Shin just needed to wait for her to return.